The field of engineering living materials (ELMs) seeks to engineer cells to form macroscopic materials with tailorable structures and properties. While the rheological properties of ELMs have been altered using synthetic biology methodology, the relationships connecting their sequence, structural, and rheological properties remain to be elucidated. Recently, our lab created centimeter-scale ELMs from Caulobacter crescentus that offer a platform to investigate this paradigm. Here, we explore how changing the elastin-like polypeptide (ELP) length within the protein matrix of this ELM impacts its microstructure and viscoelastic behavior. We demonstrate that shortening ELP produces fibers almost 2× thicker than other variants, resulting in a stiffer material at rest. Interestingly, the midlength ELP forms a complex structure with globules and multidirectional fibers with increased yield stress under flow conditions. Lengthening ELP creates thinner strands between cells with similar storage and loss moduli to those of the midlength ELP. This study begins to elucidate sequence-structure-property relationships in these ELMs and shows that they are complex with few parallels to other biocomposite models. Furthermore, it highlights that fine-tuning genetic sequences can create significant differences in rheological properties, uncovering new design principles of ELMs.

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In embedded 3D printing, the supporting gel must provide the right rheological properties to keep the ink in place. It has previously been shown that a strong and stable 3D network can be formed by particle–particle interactions of hydrophobic fumed silicas suspended in a polar solvent. Here, the rheological properties of fumed silica gels in polyethylene glycol (PEG) are investigated. The recovery properties like storage modulus, yield stress, and recovery time of the gels made of fumed silica with alkyl-chains of different lengths are studied. A very fast recovery time (0.2 s) is achieved by increasing the length of the alkyl chains on the silica surface, leading to embedded printing results with high shape accuracy. However, with the engineered supporting gel, the formation of crevasses affects the shape of the filament. Previous approaches to reduce crevasse formation include the introduction of liquid fillers to avoid such distortions, which, however, prevents the reuse of the gels and leads to increasing waste production in embedded printing. Here, it is shown that by adjusting the rheology of the inks to fit the rheology of the supporting gel, high-shape accuracy prints with ideally round-shaped filaments can be achieved without the need for liquid fillers.

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The genus Mimosa belongs to the Fabaceae family and comprises almost 400 species of herbs, shrubs and ornamental trees. The genus Mimosa is found all over the tropics and subtropics of Asia, Africa, South America, North America and Australia. Traditionally, this genus has been popular for the treatment of jaundice, diarrhea, fever, toothache, wound healing, asthma, leprosy, vaginal and urinary complaints, skin diseases, piles, gastrointestinal disorders, small pox, hepatitis, tumor, HIV, ulcers and ringworm. The review covered literature available from 1959 to 2020 collected from books, scientific journals and electronic searches, such as Science Direct, Web of Science and Google scholar. Various keywords, such as Mimosa, secondary metabolites, medicines, phytochemicals and pharmacological values, were used for the data search. The Mimosa species are acknowledged to be an essential source of secondary metabolites with a wide-ranging biological functions, and up until now, 145 compounds have been isolated from this genus. Pharmacological studies showed that isolated compounds possess significant potential, such as antiprotozoal, antimicrobial, antiviral, antioxidant, and antiproliferative as well as cytotoxic activities. Alkaloids, chalcones, flavonoids, indoles, terpenes, terpenoids, saponins, steroids, amino acids, glycosides, flavanols, phenols, lignoids, polysaccharides, lignins, salts and fatty esters have been isolated from this genus. This review focused on the medicinal aspects of the Mimosa species and may provide a comprehensive understanding of the prospective of this genus as a foundation of medicine, supplement and nourishment. The plants of this genus could be a potential source of medicines in the near future.@en

In some ports and waterways, hindered (delayed) settling of mud suspended in the water phase can be detected. Hindered settling phenomena are typically linked to a combination of sediment properties, suspended sediment concentration or density, hydrodynamic conditions, presence or absence of organic bridging between mud particles and the properties of the water phase such as salinity. Hindered settling may be desired or undesired for maintenance of the nautical depth - it might be beneficial if the properties meet the nautical bottom criteria for safe navigation and maneuvering; however, in case fast settlement and consolidation is necessary for efficient dredging, hindered settling is disadvantageous. Yield stress of mud has been extensively studied for the nautical bottom and port maintenance purposes over the last years. New rheological protocols have been developed for measuring rheological characteristics of mud deposits and analysing the structural recovery of mud. Additional knowledge has been gained from studying the role of density and organic matter and further comparison to the yield stresses measured in the laboratory and in the field. This work connects the knowledge of settling phenomena and rheology. Settling and rheological behaviour of mud from different European ports has been extensively studied. Variation of yield stress values in different ports has been studies by correlating rheological properties and settling of mud to other key sediment properties like density, mud composition, clay content and clay type, total organic carbon (TOC) and organic matter degradation. @en

Kaolin based suspensions have wide range of applications such as slurry wall, drilling fluids, adhesives, cosmetics, refractories and pharmaceuticals, due to their abundance in nature, low cost and non-swelling nature. On the other hand, the unique properties (i.e., biodegradability) of biopolymers make them suitable candidate for variety of applications including modification of clay suspensions. In this study, the rheological properties of kaolin suspensions modified with different biopolymers (xanthan gum (XG), sodium carboxymethyl cellulose (CMC), potato starch (PS), chitosan (Ch) and apple fibre (AF)) have been investigated by varying the biopolymer type, content and clay content. The main objective of the present study is to propose a substitute for the natural mud sample. Frequency sweep tests, stress ramp-up tests and time-dependent tests were performed by using the Couette geometry (coaxial cylinders) for the prepared suspensions. The rheological results showed that both viscosity and moduli were significantly influenced by adding different biopolymers into the kaolin suspensions. For instance, an increase in viscosity of modified suspensions was observed: 3 – 4 orders of magnitude by adding xanthan gum (1 wt%) or sodium carboxymethyl cellulose (5 wt%) and 6 orders of magnitude by adding apple fibre (5 wt%). Likewise, the incorporation of different biopolymers significantly affected the complex modulus of modified clay suspensions. For example, similar or higher values of complex modulus than the pure kaolin suspension were observed at low xanthan gum or sodium carboxymethyl cellulose content (0.1 wt%). In case of chitosan, the complex modulus of the modified suspensions was higher than the complex modulus of pure kaolin suspension, even at very low polymer content (1 wt%). In the case of potato starch, a decrease in complex modulus by increasing polymer content till 10 wt% was observed followed by an increase in complex modulus with polymer content. The shear rate ramp-up and ramp-down experiments showed that the time-dependent behaviour of kaolin suspensions was not strongly influenced by adding different biopolymers. This knowledge will provide a base to choose a suitable substitute for the natural mud sample.@en

Purpose
Sediment organic matter (SOM) influences settling and thus the rheological behavior of suspended particles by enhancing flocculation or reducing surface charges by forming organo-mineral complexes that facilitate particle–particle interactions in consolidating sediments. It was, therefore, assumed that the microbial degradation of SOM and its spatio-temporal variability would affect sediment rheological properties and enhance port maintenance dredging and navigability of ports and waterways.

Methods
To investigate this effect, samples were taken at six locations along a transect of 30 river kilometers through the Port of Hamburg, Germany, during nine sampling campaigns within two years. The collected samples were divided into different layers based on the differences in visual consistency and strength. For analysis of SOM degradability, the samples were incubated in the laboratory for 250 days in glass bottles under aerobic and anaerobic conditions following the evolution of gas composition (CH4, CO2) and pressure in the bottle headspace over time. Yield stress was analyzed before and after the dissolved organic matter (DOM) decay using a rheometer with Couette geometry. Standard properties of solids and pore water were also analyzed.

Results
Shear strength decreased upon SOM decay under both anaerobic and aerobic conditions. Under anaerobic conditions, organic matter decay reduced static and fluidic yield stresses to an average of 74% and 79% of the fresh sample values. Consolidated layers at lower depths showed the highest absolute decrease in fluidic yield stress of up to –110 Pa due to a larger absolute amount of degradable organic matter in these layers in connection to higher bulk density. Pronounced spatial trends with higher changes in yield stress at upstream locations and lower yield stress changes at downstream locations coincided with a decreasing gradient of SOM degradability from upstream to downstream. Seasonal trends indicated that the investigation area is impacted by temporally changing factors.

Conclusion
The availability of easily degradable organic matter significantly affects sediment strength, especially under the anaerobic conditions, even when the mass loss of organic matter mass loss is small. Seasonal variability in yield stress changes upon SOM decay indicate that the site-specific responses were modulated by overarching seasonal effects impacting the entire investigation area. It was assumed that during an anaerobic decay, the formation of gas bubbles added an additional physical component to the effect of biological SOM decay.@en

The nautical bottom (i.e., the level at which contact with a ship’s keel causes either damage or unacceptable effects on controllability and manoeuvrability of a ship) should be associated to a measurable physical characteristic. Bulk density is typically used as a criterion for nautical bottom by many ports worldwide. However, the rheological properties particularly the yield stress of mud are eventually more suitable parameters for defining a criterion for nautical bottom due to their strong correlation with the flow properties of mud and navigability. The density-yield stress correlation depends significantly on different parameters of mud such as organic matter type and content, clay type and content, particle size distribution and salinity. Therefore, a single critical value of density cannot be chosen for the nautical bottom criterion, where the above-mentioned parameters are varying from one location to another in the port. This justifies the need for a study of the rheological properties (yield stress) of mud. The main objective of this review article is to provide (i) an extensive overview of the rheological
properties (particularly yield stress) of mud from different sources, (ii) factors affecting the rheology of mud, and (iii) defining a nautical bottom for berthing areas in the port of Hamburg using a combination of yield stress and density.@en

Turbidity currents are generated as a result of various processes such as dredging and deep-sea mining. In this work, we generate a turbidity current in a lock exchange setup [1] by using 100 g/l illite, as shown in figure 1. Two different flocculant dosages (0.25 mg/g & 0.75 mg/g of clay) were used with this illite. The material was mixed in the mixing section of the lock exchange before the lock gate was opened. Experiments were done both in fresh and salt water. The samples were collected after the end of the experiment, and their rheological properties were measured using a HAAKE MARS I rheometer (Thermo Scientific, Germany). Rheological studies were carried out using Couette geometry with a gap of 1mm. The sample was gently stirred before rheological measurements. Higher yield stress values were observed in freshwater experiments compared to saltwater experiments, which can be attributed to a larger floc size in freshwater. In addition, the structural recovery of the flocs was also found to be higher in freshwater than in salt water.@en

Maintenance of the nautical depth in the seaport of Emden, Germany, is achieved by re-circulation of fluid mud using a trailing suction hopper dredger. Continued re-circulation has proven to maintain low settling rates and to keep yield stresses of re-circulated fluid mud below 50-100 Pa, in combination with densities of 1.15- 1.2 t/m³ enabling safe navigation through these layers. It is assumed that low-density extracellular polymeric substances (EPS), produced by a highly adapted microbial community, are responsible for the desired effect of keeping fine-grained sediment in suspension and that the regular contact with the oxygenated water phase during recirculation dredging supports thriving of this community. Climate change models have indicated increased future discharge of fresh water from the hinterland into the saline port of Emden. It is hypothesized that increased freshwater discharge alters the composition and activity of the microbial community and hence changes the prerequisites for maintaining the currently favourable properties of fluid mud. In this paper we evaluate this hypothesis by elucidating the main factors governing the success of the current practice of re-circulation dredging in the Port of Emden by means of field and laboratory investigations. Initial results obtained in this ongoing research suggest that the low yield stresses of fluid mud in the Port of Emden are not the result of a specialized microbial community producing high concentrations of EPS, but can be solely attributed to a reduction in density as achieved by re-circulation dredging. Secondly, it appears that future possible increases in the share of freshwater do not affect the sediment’s rheological response, settling behaviour and concentration of extracellular polymeric substances and will hence not adversely impact the maintenance of the nautical depth. @en

The presence of clay-organic flocs in cohesive mud results in a complex rheological behavior of mud, including viscoelasticity, shear-thinning, thixotropy and two-step yielding. In this study, the effect of microbial degradation of organic matter on the rheological properties of mud samples, collected from different ports, was examined. The mud samples were collected from five different European ports (Port of Antwerp (PoA), Port of Bremerhaven (PoB), Port of Emden (PoE), Port of Hamburg (PoH) and Port of Rotterdam (PoR)), displaying varying sediment properties. The rheological analysis of fresh and degraded mud samples was performed with the help of several tests, including stress ramp-up tests, amplitude sweep tests, frequency sweep tests, time-dependent tests and structural recovery tests. The results showed: (i) a significant decrease in yield stresses and complex modulus after organic matter degradation for mud samples from PoA, PoH and PoR, (ii) a negligible change in rheological properties (yield stresses, crossover amplitude and complex modulus) for mud samples from PoB, and (iii) a significant increase in rheological properties for mud samples from PoE. For time-dependent tests, mud samples from PoB showed a substantial increase in hysteresis (~50% mean value) as compared to the changes in yield stresses and crossover amplitude. The analysis of gas production during degradation of organic matter showed a (i) significant release of carbon per g dry matter for mud samples from PoA, PoH and PoR, (ii) lower carbon release per g dry matter for mud samples from PoB, and (iii) a negligible carbon release per g dry matter for mud samples from PoE, which corresponded well with the change in rheological properties.@en

A large fraction of population is suffering from waterborne diseases due to the contaminated drinking water. Both anthropogenic and natural sources are responsible for water contamination. Revolution in industrial and agriculture sectors along with a huge increase in human population has brought more amount of wastes like heavy metals, pesticides and antibiotics. These toxins are very harmful for human health, therefore, it is necessary to sense their presence in environment. Conventional strategies face various problems in detection and quantification of these pollutants such as expensive equipment and requirement of high maintenance with limited portability. Recently, nanostructured devices have been developed to detect environmental pollutants. Polymeric nanocomposites have been found robust, cost effective, highly efficient and accurate for sensing various environmental pollutants and this is due to their porous framework, multi-functionalities, redox properties, great conductivity, catalytic features, facile operation at room temperature and large surface area. Synergistic effects between polymeric matrix and nanomaterials are responsible for improved sensing features and environmental adaptability. This review focuses on the recent advancement in polymeric nanocomposites for sensing heavy metals, pesticides and antibiotics. The advantages, disadvantages, operating conditions and future perspectives of polymeric nanocomposites for sensing toxic pollutants have also been discussed.

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In this study, nickel oxide–Y2O3-doped ZrO2 (NiO-YSZ) composite powder as an anode material was synthesized using a cost-effective combustion method for high-temperature solid oxide fuel cell (SOFC). Further, the effects of sintering temperatures (1200, 1300, and 1400 °C) were studied for its properties in relation to the SOFC performance. The prepared and sintered NiO-YSZ materials were characterized for their surface morphology, composition, structure, and conductivity. The cubic crystalline nature of NiO and YSZ was sufficed by X-ray diffraction, and SEM images revealed an increase in the densification of microstructure by an increase in the sintering temperature. EDX spectrum confirmed the presence of nickel, yttrium, and zirconia without any impurity. Conductivity measurements, under a hydrogen environment, revealed that NiO-YSZ, sintered at 1400 °C, exhibits better conductivity compared to the samples sintered at lower temperatures. Electrochemical performance of button-cells was also evaluated and peak power density of 0.62 Wcm−2 is observed at 800 °C. The citrate combustion method provided peak performance for cells containing anode sintered at 1200 °C, which was previously reported at higher sintering temperatures. Therefore, the citrate combustion method is found to be a suitable route to synthesize NiO-YSZ at low sintering temperature.@en

The nautical bottom (the level at which contact with a ship’s keel causes either damage or unacceptable effects on controllability and manoeuvrability of a ship) should be associated to a measurable physical characteristic. Bulk density is typically used as a criterion for nautical bottom by many ports worldwide. However, the rheological properties particularly the yield stress of mud would be better parameters for defining a criterion for nautical bottom due to their strong correlation with the flow properties of mud and navigability. The density-yield stress correlation depends significantly on different parameters of mud such as organic matter type and content, clay type and content, particle size distribution and salinity. Therefore, a single critical value of density cannot be chosen for the nautical bottom criterion in a port like Port of Hamburg, where the above mentioned parameters are varying from one harbour location to another. This justifies the need for a study of the rheological properties (yield stress) of mud in Port of Hamburg.@en

Rapid industrial development, vehicles, domestic activities and mishandling of garbage are the main sources of pollutants, which are destroying the atmosphere. There is a need to continuously monitor these pollutants for the safety of the environment and human beings. Conventional instruments for monitoring of toxic gases are expensive, bigger in size and time-consuming. Hybrid materials containing organic and inorganic components are considered potential candidates for diverse applications, including gas sensing. Gas sensors convert the information regarding the analyte into signals. Various polymeric/inorganic nanohybrids have been used for the sensing of toxic gases. Composites of different polymeric materials like polyaniline (PANI), poly (4-styrene sulfonate) (PSS), poly (3,4-ethylene dioxythiophene) (PEDOT), etc. with various metal/metal oxide nanoparticles have been reported as sensing materials for gas sensors because of their unique redox features, conductivity and facile operation at room temperature. Polymeric nanohybrids showed better performance because of the larger surface area of nanohybrids and the synergistic effect between polymeric and inorganic materials. This review article focuses on the recent developments of emerging polymeric/inorganic nanohybrids for sensing various toxic gases including ammonia, hydrogen, nitrogen dioxide, carbon oxides and liquefied petroleum gas. Advantages, disadvantages, operating conditions and prospects of hybrid composites have also been discussed.

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Organogelation is one of the most promising techniques to replace unhealthy saturated fats in foods, guaranteeing a similar texture but with the use of healthy unsaturated oils. Nevertheless, the number of food grade gelators is not high, and the discovery of new agents is still due to "serendipity". Among the different gelators investigated in the literature, fatty alcohols, i.e., aliphatic hydrocarbons with a hydroxyl group, represent an interesting alternative. Within this context, a mixture of long chain alcohols, commercially known as Policosanol, seems particularly promising. Policosanol can be extracted from natural sources such as sugarcane, beeswax, wheat germ, and rice bran. Policosanol is very effective in structuring edible oils even at a very low concentration (0.1%) and has positive health effects on the cardio-circulatory system and cholesterol levels. Therefore, structured vegetable oils can be obtained through the use of edible healthy gelators (i.e., Policosanol). The oleogels developed with Policosanol might be used as substitutes for traditional hard fats or as novel structured vegetable oil systems with controlled rheological properties. The rheological, microscopic, and sensory properties of fatty alcohol oleogels are discussed in this chapter, as well as their potential use for producing new foods and vehicles for the controlled release of nutraceutical compounds.

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Purpose
The presence of organic matter in cohesive sediment results in the formation of clay-organic flocs, which eventually impart complex rheological behavior including shear-thinning, viscoelasticity, thixotropy and two-step yielding to mud. In this study, the influence of microbial degradation of sediment organic matter on the rheological properties of mud samples, having similar densities, was examined.

Materials and methods
Mud samples were collected from three different locations in the Port of Hamburg, Germany, displaying varying organic matter content. The rheological analysis of fresh and degraded mud samples was performed with the help of several tests including stress ramp-up tests, amplitude sweep tests, frequency sweep tests, time-dependent tests, and structural recovery tests.

Results and discussion
The results showed a significant decrease in rheological properties including yield stresses, complex modulus, etc. for degraded mud samples as compared to the fresh mud samples. The slopes of the line, correlating the change (degraded − fresh) in the above-mentioned rheological properties as a function of the same rheological property of the fresh mud, varied within the range of −0.28 to −0.49. The structural recovery tests displayed a better recovery (i.e., stronger system) in mud after the pre-shearing step for the degraded mud samples as compared to the fresh mud samples. The effect of degradation time on the rheological properties of mud samples showed two critical time periods (3 days and 150 days) after which a significant change in rheological properties of mud samples was observed.

Conclusions
This study provided a useful understanding about the influence of organic matter degradation on the rheological properties of mud, which can be used to optimize sediment management strategies in ports and waterways.@en

Organic–inorganic nanohybrids-based polymer nanocomposites are made up of two different components, and these hybrids attained great attention over last decades due to their diversified framework and fascinating features. These nanohybrids possess synergistic characteristics of both organic and inorganic substances. Different synthetic routes are used to synthesize these materials with enhanced morphology, tunable features, and fine nanostructures. This chapter focuses on various synthetic routes for fabrication of organic–inorganic-based nanopolymeric composites. Synthetic strategies and protocols of different routes have been described in details. We have also discussed the advantages and limitations of all synthetic methods in details.

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Mud, a cohesive material, consists of water, clay minerals, sand, silt and small quantities of organic matter (i.e., biopolymers). Amongst the different mud layers formed by human or natural activities, the fluid mud layer found on top of all the others is quite important from navigational point of view in ports and waterways. Rheological properties of fluid mud layers play an important role in navigation through fluid mud and in fluid mud transport. However, the rheological properties of mud are known to vary as a function of sampling location within a port, sampling depth and sampling location across the globe. Therefore, this variability in rheolog-ical fingerprint of mud requires a detailed and systematic analysis. This chapter presents two different sampling techniques and the measured rheological properties of mud, obtained from laboratory experiments. The six protocols used to measure the yield stresses are detailed and compared. Furthermore, the empirical or semi-empirical models that are commonly used to fit rheological experimental data of such systems are presented. The influence of different factors such as density and organic matter content on the rheological behavior of mud is discussed. The fluidic yield stress of mud samples was observed to vary from 0.2 Pa to 500 Pa as a function of density and organic matter content.@en

Diverse applications of polymeric materials have prompted development of eco-friendly, efficient, and economical materials. These characteristics can be obtained by incorporating appropriate fillers in the polymeric matrix. The objective of this work is to investigate impact of aqueous glycerol (Gly) treated rice husk (RH) on surface mechanical properties of produced biocomposites. RH was treated with aqueous Gly (75 wt%) and compounded with low density polyethylene (LDPE) at different loadings (10, 20, and 30 wt%). The resulting mixture was thermally pressed in molds to fabricate biocomposites. Surface mechanical properties such as elastic modulus, hardness, creep rate, and plasticity of biocomposites reinforced with untreated and treated RH were investigated using nanoindenter. Experimental values depicted that hardness (H) and elastic modulus (E_s) of treated biocomposites were higher than untreated ones. Treated biocomposites showed the noticeable improvement in elastic modulus by 24 and 37% compared to untreated biocomposites at 20 wt% loading and neat LDPE, respectively. Reductions in the creep rate by 20 and 14% were observed for untreated and treated biocomposites, respectively, in comparison to the neat LDPE. H/E ratio was increased by 23 and 18% for treated and untreated biocomposites, respectively, as compared to virgin LDPE. Furthermore, mechanical and structural properties of untreated and treated RH are reported based on nanoindentation response and Fourier transform infrared spectroscopy (FTIR) techniques The study indicated that aqueous glycerol pretreatment can partially strip off non-cellulosic constituents from lignocellulose matrix to generate cellulose-rich pulp for engineered composite applications.@en