Search

We highlight camphene-camphor-polypropylene plastic as a useful material for self-propelled objects that show aggregation while floating on a water surface. We consider self-propelled rods as an example of aggregation of objects characterized by non-trivial individual shapes with low-symmetry interactions between them. The motion of rods made of the camphene-camphor-polypropylene plastic is supported by dissipation of the surface-active molecules. The physical processes leading to aggregation and the mathematical model of the process are discussed. We analyze experimental data of aggregate formation dynamics and relate them to the system's properties. We speculate that the aggregate structure can be represented as a string of symbols, which opens the potential applicability of the phenomenon for information processing if objects floating on a water surface are regarded as reservoir computers.

The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, and a structure of a multi-component polymer-containing material. Determination of a relation between the structure of a complex material, the structure and properties of its constituent elements, and the rheological properties of the material as a whole is the subject of structural rheology-a valuable tool for the development and study of novel materials. This work summarizes the author's structural-rheological studies of complex polymer materials for determining the conditions and rheo-manifestations of their micro- and nanostructuring. The complicated chemical composition of macromolecular chains and its role in polymer structuring via block segregation and cooperative hydrogen bonds in melt and solutions is considered using tri- and multiblock styrene/isoprene and vinyl acetate/vinyl alcohol copolymers. Specific molecular interactions are analyzed in solutions of cellulose; its acetate butyrate; a gelatin/carrageenan combination; and different acrylonitrile, oxadiazole, and benzimidazole copolymers. A homogeneous structuring may result from a conformational transition, a mesophase formation, or a macromolecular association caused by a complex chain composition or specific inter- and supramolecular interactions, which, however, may be masked by macromolecular entanglements when determining a rheological behavior. A heterogeneous structure formation implies a microscopic phase separation upon non-solvent addition, temperature change, or intense shear up to a macroscopic decomposition. Specific polymer/particle interactions have been examined using polyethylene oxide solutions, polyisobutylene melts, and cellulose gels containing solid particles of different nature, demonstrating the competition of macromolecular entanglements, interparticle interactions, and adsorption polymer/particle bonds in governing the rheological properties. Complex chain architecture has been considered using long-chain branched polybutylene-adipate-terephthalate and polyethylene melts, cross-linked sodium hyaluronate hydrogels, asphaltene solutions, and linear/highly-branched polydimethylsiloxane blends, showing that branching raises the viscosity and elasticity and can result in limited miscibility with linear isomonomer chains. Finally, some examples of composite adhesives, membranes, and greases as structured polymeric functional materials have been presented with the demonstration of the relation between their rheological and performance properties.

This paper covers the design of binder formulations and technology for low-energy building materials based on alkaline aluminosilicate binders developed for special uses. The microstructure of the binders was investigated using scanning electron and atomic force microscopy examination techniques. The identification of phase compositions was performed by means of X-ray diffraction. The degree of binding of the alkali metal ions within the binder was determined with the help of chemical analysis of the pore fluid. Structure formation depending upon binder mix design and curing conditions was also studied. Some examples of the manufacture and application of binder-based glues and adhesives, including those developed for heat insulation and fire prevention, are discussed. The advantages of binder-based temperature-insulating composite materials compared with traditionally used materials are highlighted.

Spray-drying is a popular and well-known "drying tool" for engineers. This perspective highlights that, beyond this application, spray-drying is a very interesting and powerful tool for materials chemists to enable the design of multifunctional and hybrid materials. Upon spray-drying, the confined space of a liquid droplet is narrowed down, and its ingredients are forced together upon "falling dry." As  detailed in this article, this enables the following material formation strategies either individually or even in combination: nanoparticles and/or molecules can be assembled; precipitation reactions as well as chemical syntheses can be performed; and templated materials can be designed. Beyond this, fragile moieties can be processed, or "precursor materials" be prepared. Post-treatment of spray-dried objects eventually enables the next level in the design of complex materials. Using spray-drying to design (particulate) materials comes with many advantages-but also with many challenges-all of which are outlined here. It is believed that multifunctional, hybrid materials, made via spray-drying, enable very unique property combinations that are particularly highly promising in myriad applications-of which catalysis, diagnostics, purification, storage, and information are highlighted., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Graphene oxide (GO) has proved itself as a nanomaterial capable of acting as a surfactant by lowering the interfacial tension of the oil-water interface due to its polar oxygen groups. However, the surfactant behavior of the pure graphene sheet─since prevention of edge oxidation in experimental setups is nontrivial─is still an unresolved issue in graphene research despite significant progress in the field in recent years. Here, we conduct both atomistic and coarse-grained simulations to demonstrate that─surprisingly─even pristine graphene, which only consists of hydrophobic carbon atoms, is attracted to the octanol-water interface and consequently reduces its surface tension by 2.3 k B T /nm 2 or about 10 mN/m. Interestingly, the location of the free energy minimum is not precisely at the oil-water interface itself but is rather buried about two octanol layers into the octanol phase, being about 0.9 nm from the water phase. We demonstrate that the observed surfactant behavior is purely entropically driven and can be attributed to the unfavorable lipid-like structuring of octanol molecules at the free octanol-water interface. In essence, graphene enhances the inherent lipid-like behavior of octanol at the water interface rather than directly acting as a surfactant. Importantly, graphene does not display surfactant-like behavior in corresponding Martini coarse-grained simulations of the octanol-water system since the free liquid-liquid interface loses essential structure at the lower coarse-grained resolution. However, a similar surfactant behavior is recovered in coarse-grained simulations of longer alcohols such as dodecan-1-ol and hexadecan-1-ol. The observed discrepancies at different model resolutions enable us to construct a comprehensive model of the surfactant behavior of graphene at the octanol-water interface. The here-gained insights may facilitate the broader utilization of graphene in numerous domains of nanotechnology. Furthermore, since a drug's octanol-water partition coefficient is a crucial physicochemical parameter in rational drug discovery, we also believe that the universality of the here-illustrated entropic surfactant behavior of planar molecules deserves special attention in the drug design and development field.

There are various types of gel materials used in a wide range of fields, and their gelation mechanisms are extremely diverse. Furthermore, in the case of hydrogels, there exist some difficulties in understanding complicated molecular mechanisms especially with water molecules interacting through hydrogen bonding as solvents. In the present work, the molecular mechanism of the structural formation of fibrous super-molecular gel by the low molecular weight gelator, N-oleyl lactobionamide/water mixture was elucidated using the broadband dielectric spectroscopy (BDS) method. The dynamic behaviors observed for the solute and water molecules indicated hierarchical structure formation processes in various time scales. The relaxation curves obtained at various temperatures in the cooling and heating processes showed relaxation processes respectively reflecting the dynamic behaviors of water molecules in the 10 GHz frequency region, solute molecules interacting with water in MHz region, and ion-reflecting structures of the sample and electrode in kHz region. These relaxation processes, characterized by the relaxation parameters, showed remarkable changes around the sol-gel transition temperature, 37.8 °C, determined by the falling ball method and over the temperature range, around 53 °C. The latter change suggested a structure formation of rod micelles appearing as precursors before cross-linking into the three-dimensional network of the supramolecular gels. These results clearly demonstrate how effective relaxation parameter analysis is for understanding the gelation mechanism in detail., Competing Interests: The authors declare no conflict of interest.

Amyloid fibrils represent the structural endpoint on the energetic (mis)folding landscape of very many proteins. Physiologically, amyloid fibrils are observed as a characteristic hallmark in misfolding diseases often associated with degenerative and neurodegenerative disorders. In the beginning of the scientific discussion, the focus is laid on the fibrillar state, but over the time it becomes increasingly clear that low molecular weight and transient aggregates are of crucial importance for pathological mechanisms. Structural studies find different intra- and intermolecular contacts for the most well-studied peptide amyloid β (Aβ) depending on the stage of fibrillation. In particular, the contact between residues phenylalanine 19 (F19) and leucine 34 (L34) seems to be highly conserved, suggesting that it must be of particular significance for Aβ misfolding and possibly the pathological properties of the peptide. This review aims to highlight the rational and the usefulness of point mutations in Aβ peptides and their impact on the critical interstrand contact F19-L34 depending on the stage of fibrillation. While the amyloid structure of Aβ is very robust against quite a few modifications, the toxicity of mutated Aβ molecules highly depends on the F19-L34 contact., (© 2023 The Authors. Macromolecular Bioscience published by Wiley-VCH GmbH.)

This study explored unprocessed high-carbon biomass fly ash (BFA) in alkali-activated materials (AAM) with less alkaline Na 2 CO 3 as the activator. In this paper, the effects of the Na 2 CO 3 /Na 2 SiO 3 (C/S) ratio and curing temperature (40 °C and 20 °C) on the setting time, structure formation, product synthesis, and physical-mechanical properties of alkali-activated BFA pastes were systematically investigated. Regardless of curing temperature, increasing the C/S ratio increased the density and compressive strength of the sample while a decrease in water absorption. The higher the curing temperature, the faster the structure evolution during the BFA-based alkaline activation synthesis process and the higher the sample's compressive strength. According to XRD and TG/DTA analyses, the synthesis of gaylussite and C-S-H were observed in the sample with an increasing C/S ratio. The formation of the mentioned minerals contributes to the compressive strength growth of alkali-activated BFA pastes with higher C/S ratios. The findings of this study contribute to the applicability of difficult-to-recycle waste materials such as BFA and the development of sustainable BFA-based AAM.

One of the materials that attracts attention as a potential material for membrane formation is ultrahigh molecular weight polyethylene (UHMWPE). One potential material for membrane formation is ultrahigh molecular weight polyethylene (UHMWPE). The present review summarizes the results of studies carried out over the last 30 years in the field of preparation, modification and structure and property control of membranes made from ultrahigh molecular weight polyethylene. The review also presents a classification of the methods of membrane formation from this polymer and analyzes the conventional (based on the analysis of incomplete phase diagrams) and alternative (based on the analysis of phase diagrams supplemented by a boundary line reflecting the polymer swelling degree dependence on temperature) physicochemical concepts of the thermally induced phase separation (TIPS) method used to prepare UHMWPE membranes. It also considers the main ways to control the structure and properties of UHMWPE membranes obtained by TIPS and the original variations of this method. This review discusses the current challenges in UHMWPE membrane formation, such as the preparation of a homogeneous solution and membrane shrinkage. Finally, the article speculates about the modification and application of UHMWPE membranes and further development prospects. Thus, this paper summarizes the achievements in all aspects of UHMWPE membrane studies.

Finding new ways of recycling production waste to improve the characteristics of various building materials is an urgent scientific task. This article substantiates the possibility of the disposal of fly ash in the composition of soil concrete, which is used in the construction of the structural layers of road pavements, foundations of buildings and structures, as well as sites for various purposes. The scientific novelty lies in the fact that the structure formation of soil concretes based on loam and fly ash and modified with a stabilizing additive is being studied for the first time. It was found that the investigated fly ash, according to its hydraulic properties, is classified as latent active and can be introduced into the compositions of road soil concrete modified with additives of various resources. The effectiveness of the complex method of stabilization, due to changes in soil properties as a result of the use of the binding and stabilizing additives of polymer nature "Kriogelit", is shown. It was found that the optimal content of binder and fly ash in the samples was 8 and 10 wt.%, respectively. It was established that the use of the stabilizing additive "Kriogelit" makes it possible to obtain soil concrete with the highest strength (compressive strength 2.5 MPa, flexural strength 0.5 MPa) and frost resistance of at least F15. The microstructure, the degree of dehydration and carbonization, and the phase composition of the initial raw mixtures and soil concretes stabilized with the addition of "Kriogelit" were studied by methods of scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. It was shown that organo-mineral complexes, with the participation of polymer and montmorillonite, are formed in stabilized soil concrete. It was revealed that structure formation is accompanied by the physical adsorption of the polymer on active centers of silicate minerals, carbonization, and hydration-dehydration processes. It was found that the reason for the increase in the strength of stabilized soil concretes is the hydrophobization of the porous structure of minerals, as well as the formation of calcium oxide silicate and dicalcium hydrated silicate. By the method of performing biotests with the test objects Daphnia magna Straus and Chlorella vulgaris Beijer, it was proven that the developed road concretes modified with the stabilizing additive "Kriogelit" do not have an acute toxic effect on the test objects and are safe for the environment and human health.

The possibility of improving the properties of porous geopolymer materials based on ash and slag waste from thermal power plants by adjusting their chemical composition is considered. An X-ray phase analysis of ash and slag wastes was carried out, the geopolymers' precursor compositions were calculated, and additives to correct their chemical composition were selected. The samples were synthesized and their physical and mechanical properties (density, porosity, compressive strength, thermal conductivity) were analyzed. The micro- and macro-structure of the samples and the pore distribution of the obtained geopolymers were studied and pore-distribution histograms were obtained. The influence of Si:Al ratio on structural changes was described. The geopolymers' phase composition was studied, consisting of an amorphous phase and high quartz and mullite. A conclusion about the applicability of this method for obtaining high-quality porous geopolymers was made.

Cellulose was treated with supercritical water at 668 K and 25 MPa for 0.04 s in this study. The cellulose/water system was transparent at room temperature for a while after supercritical water treatment before a precipitate gradually appeared over several hours. The precipitation process was monitored by synchrotron X-ray scattering. The scattering functions of fractal systems and flat-like structures were utilized to explain the experimentally observed small-angle scattering profiles. Immediately after supercritical water treatment, the cellulose appeared to dissolve with a fractal dimension D of approximately 1, indicating that the cellulose molecules were rigid, followed by aggregation into a 5-nm-thick flat-like structure. The flat-like structure was determined to be similar to the molecular sheets observed during the early stages of precipitation in the cellulose/aqueous sodium hydroxide and cellulose/aqueous lithium hydroxide/urea systems. Resultant regenerated cellulose had high crystallinity, large crystal size, and a low degree of polymerization., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

We study the statistical mechanics of binary systems under the gravitational interaction of the Modified Newtonian Dynamics (MOND) in three-dimensional space. Considering the binary systems in the microcanonical and canonical ensembles, we show that in the microcanonical systems, unlike the Newtonian gravity, there is a sharp phase transition, with a high-temperature homogeneous phase and a low-temperature clumped binary one. Defining an order parameter in the canonical systems, we find a smoother phase transition and identify the corresponding critical temperature in terms of the physical parameters of the binary system.

It is known that tumor cells have a lower pH compared to normal cells. We have designed peptides that have no definite structure at neutral pH but at lower pH penetrate into the cell membrane by forming an α-helix structure and thus damage tumor cells selectively. These peptides were designed by combining a pH-responsive artificially designed α-helix structure and a flanking sequence that controls membrane insertion. In aqueous solution, some of these peptides were found to be unstructured at neutral pH and helical at acidic pH and showed destruction ability against negatively charged liposomes only at acidic pH. In living cells, one of the designed peptides induced 40% cell death against cervical cancer HeLa and breast cancer MCF-7 cells, while almost no cell death was observed against normal cells. The designed peptide can thus cause tumor cell death without side effects by responding to the peculiar environment of the cell membrane.

The physical and mechanical characteristics of expanded-clay lightweight concrete based on a supersulfated binder in comparison with lightweight concrete based on ordinary Portland cement were studied. In replacing CEM 32.5 with a supersulfated binder of 6000 cm 2 /g specific surface, one can increase the tensile strength in bending up to 20% and can increase the ratio of the tensile strength in bending to the compressive strength that indicates the crack resistance increase of concrete. Compressive strengths at the age of 28 days were equal to 17.0 MPa and 16.6 MPa for the supersulfated binder of 3500 cm 2 /g specific surface and CEM 32.5, respectively. Shrinkage deformation of hardening concrete, indicators of fracture toughness, frost resistance, and thermal conductivity were determined during the experimental works. The coefficient of thermal conductivity decreased up to 12% compared to the use of CEM 32.5. An enhancement in concrete properties was associated with the increase of supersulfated binder fineness.

High-pressure processing (HPP) has been the most adopted nonthermal processing technology in the food industry with a current ever-growing implementation, and meat products represent about a quarter of the HPP foods. The intensive research conducted in the last decades has described the molecular impacts of HPP on microorganisms and endogenous meat components such as structural proteins, enzyme activities, myoglobin and meat color chemistry, and lipids, resulting in the characterization of the mechanisms responsible for most of the texture, color, and oxidative changes observed when meat is submitted to HPP. These molecular mechanisms with major effect on the safety and quality of muscle foods are comprehensively reviewed. The understanding of the high pressure-induced molecular impacts has permitted a directed use of the HPP technology, and nowadays, HPP is applied as a cold pasteurization method to inactive vegetative spoilage and pathogenic microorganisms in ready-to-eat cold cuts and to extend shelf life, allowing the reduction of food waste and the gain of market boundaries in a globalized economy. Yet, other applications of HPP have been explored in detail, namely, its use for meat tenderization and for structure formation in the manufacturing of processed meats, though these two practices have scarcely been taken up by industry. This review condenses the most pertinent-related knowledge that can unlock the utilization of these two mainstream transformation processes of meat and facilitate the development of healthier clean label processed meats and a rapid method for achieving sous vide tenderness. Finally, scientific and technological challenges still to be overcome are discussed in order to leverage the development of innovative applications using HPP technology for the future meat industry., (© 2020 Institute of Food Technologists®.)

A hierarchical nanoporous layer (HNL) can be formed on the silicate glass surface by simple alkali etching. Though it reportedly exhibits various useful functions, such as superhydrophilicity, optical anti-reflection, and material impregnation, the principle of its formation still remains unclear. In this study, HNL formation behavior was experimentally investigated while using scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) to clarify the role of boron contained in glass. As a result, it was found that HNL formation was significantly promoted by boron, which was rapidly eluted prior to alkali and alkaline earth metals. This suggests that boron, which forms the skeleton structure of glass together with Si and O, elutes to partially decompose the skeleton, and extends the elution route for HNL formation.

In situ synchrotron studies of structure and phase formation dynamics in mechanically activated (t = 7 min, power density 40 g) and mechanically activated with subsequent irradiation by γ-quanta 60 Co powder mixture (Ti 64 wt% + Al) during high-temperature synthesis by the method of thermal explosion using induction heating are described. In situ high-temperature synthesis was carried out on the created experimental complex adapted for synchrotron X-ray diffraction methods. The sequence of formation and time-temperature interval of the metastable and main phases were determined. The impact of preliminary mechanical activation and of γ-irradiation on the macrokinetic parameters of the synthesis were studied experimentally in situ. It has been established that the impact of γ-irradiation on the mechanically activated powder mixture of the composition Ti 64 wt% + Al leads to a change in the thermal parameters of combustion: the maximum synthesis temperature and the burning rate decrease. The heating rate for the non-irradiated mixture is 204.8 K s -1 and that for the irradiated mixture is 81.6 K s -1 . The dependences of mass fractions of the synthesized compounds on time and temperature were calculated from the stage of preheating until completion of the thermal explosion. A single-phase equilibrium product of the composition γ-(TiAl) is formed in γ-irradiated mechanically activated mixture when the system reaches maximum temperature. The synthesized product of the mechanically activated mixture without γ-irradiation contains 72% γ-(TiAl); TiAl 3 (26%) and residual Ti (2%) are also observed.

Controlling the structure formation of gold nanoparticle aggregates is a promising approach towards novel applications in many fields, ranging from (bio)sensing to (bio)imaging to medical diagnostics and therapeutics. To steer structure formation, the DNA-DNA interactions of DNA strands that are coated on the surface of the particles have become a valuable tool to achieve precise control over the interparticle potentials. In equilibrium approaches, this technique is commonly used to study particle crystallization and ligand binding. However, regulating the structural growth processes from the nano- to the micro- and mesoscale remains elusive. Here, we show that the non-equilibrium structure formation of gold nanoparticles can be stirred in a binary heterocoagulation process to generate nanoparticle clusters of different sizes. The gold nanoparticles are coated with sticky single stranded DNA and mixed at different stoichiometries and sizes. This not only allows for structural control but also yields access to the optical properties of the nanoparticle suspensions. As a result, we were able to reliably control the kinetic structure formation process to produce cluster sizes between tens of nanometers up to micrometers. Consequently, the intricate optical properties of the gold nanoparticles could be utilized to control the maximum of the nanoparticle suspension extinction spectra between 525 nm and 600 nm., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Solvent evaporation in soft-matter solutions (solutions of colloidal particles, polymers, and their mixtures) is an important process in material making and in the printing and coating industries. The solvent-evaporation process determines the structure of materials and strongly affects their performance. Solvent evaporation involves many physicochemical processes: flow, diffusion, crystallization, gelation, glass transition, etc. and is quite complex. Here, recent progress in this important process is reported, with a special focus on theoretical and simulation studies., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Oligodendrocytes are the myelin-producing cells of the central nervous system that are responsible for electrically insulating axons to speed the propagation of electrical impulses. A striking feature of oligodendrocyte development within white matter is that the cell bodies of many oligodendrocyte progenitor cells become organised into discrete linear arrays of three or more cells before they differentiate into myelin-producing oligodendrocytes. These linear arrays align parallel to the direction of the axons within white matter tracts and are believed to play an important role in the co-ordination of myelination. Guided by experimental data on the abundance and composition of linear arrays in the corpus callosum of the postnatal mouse brain, we construct discrete and continuous models of linear array generation to specifically investigate the relative influence of cell migration, proliferation, differentiation and death of oligodendroglia upon the genesis of linear arrays during early postnatal development. We demonstrate that only models that incorporate significant cell migration can replicate all of the experimental observations on number of arrays, number of cells in arrays and total cell count of oligodendroglia within a given area of the corpus callosum. These models are also necessary to accurately reflect experimental data on the abundance of linear arrays composed of oligodendrocytes that derive from progenitors of different clonal origins., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The pH-sensitive hydrogels composed of sodium caseinate (SC) and N,O-carboxymethyl chitosan (NOCC) were prepared and a new method to characterize the gelation process was presented in this work. Reological tests suggested that RSC/NOCC=3/7 (the weight ratio of SC and NOCC) was the best ratio of hydrogel. The well-developed three-dimensional network structures in the hydrogel were confirmed by AFM. Two structural parameters, tIS and tCS, denoted as the initial and critical structure formation time, respectively, were used to provide an exact determination of the start of structure formation and description of gelation process. The gelation process strongly depended on temperature changes, a high temperature resulted in an early start of gelation. The non-kinetic model suggested the higher activation energy in the higher temperatures was disadvantageous to structure formation, and vice versa. Due to the smart gel reported here was very stable at room temperature, we believed that the gel is required for applications in drug delivery or could be exploited in the development of potential application as molecular switches in the future., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Smart capillary suspensions are used to fabricate macroporous solids with unique features regarding porosity and mechanical strength from a wide range of materials, including carbon layers and polyethylene membranes, even if sintering or high-temperature treatment is not feasible. High-strength porous ceramics are obtained, tailoring neck and pore shape via controlled deposition of fine particles at the sintering necks., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Spray drying processes were utilized for the production of hierarchical materials with defined structures. The structure formation during the spray drying process and the micromechanical properties of the obtained aggregates depend on the particle-particle interactions, the primary particle size and morphology as well as the process parameters of the spray drying process. Hence, the effect of different primary particle systems prepared as stable dispersions with various surface modifications were investigated on the colloidal structure formation and the micromechanical properties of silica particles as model aggregates and compared to theoretical considerations. The obtained results show that the structure formation of aggregates during the spray drying process for stable suspensions is almost independent on the functional groups present at the particle surface. Further, the mechanical properties of these aggregates differ considerably with the content of the bound ligand. This allows the defined adjustment of the aggregate properties, such as the strength and surface properties, as well as the formation of defined hierarchical aggregate structures., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Diatom silica cell walls present an intriguing application of biomineralization in a single celled organism. The ability of diatoms to make an enormous variety of silica structures on the nano- to micro-scale is unparalleled in nature. The process is a whole-cell endeavor, involving diverse cellular components that coordinate "bottom up" and "top down" structure formation processes to reproducibly convert genetic information into physical structure. The study of silicification has been similarly all encompassing, involving the application of diverse analytical techniques to examine different aspects of the process. This review highlights the application of different approaches used to study silicification and the insights they have provided, and documents the progress that has been made. The current status offers the possibility of major breakthroughs in our understanding, by enabling a more widespread identification of genes involved, and direct testing of the role these genes play by genetic manipulation., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The salivary gland is characterized by ramified epithelial branches, a specific tissue structure responsible for saliva production and regulation. To regenerate the salivary gland function, it is important to establish the tissue structure. Chitosan is a deacetylated derivative of chitin with wide biomedical applications. Because of its deacetylated nature, chitosan has different properties when prepared with different degrees of deacetylation (DDA). However, the impact of chitosan DDA on the effect of regulating tissue structure formation remains unexplored. In this study, the embryonic murine submandibular gland (SMG) was used as a model to investigate the role of chitosan DDA in regulating tissue structure formation of the salivary gland. When chitin substrates with different DDA were used, the branching numbers of cultured SMG explants changed. Similar effects were observed in the culture with chitosan prepared using different degrees of acetylation. The mRNA expressions of type I and type III collagen were elevated in SMG explants with enhanced branching morphogenesis, as was the protein level. In addition to the amounts of collagen, type I and type III collagen fibers were spatially present in the epithelial-mesenchymal junction of developing branches in the culture with chitosan of a specific range of DDA. The branch-promoting effect of chitosan DDA was abolished when SMG explants were treated with collagenase, both early in the stage of branch initiation and with the establishment of the branching structure. The branch-promoting effect of chitosan DDA disappeared when antisense oligonucleotides were applied to specifically block type III collagen. This study demonstrates for the first time that DDA of chitosan affects tissue structure formation. The different proportions of side-chain components of chitin derivatives regulate structural formation of cultured SMG, indicating that DDA is an important parameter using chitosan as a biomaterial for tissue structure formation of the salivary glands., (Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Three types of population growth and development of chemotaxic motile bacteria Escherichia coli on semi-solid nutrient media are investigated: a) stable development - circular symmetrical waves; b) bursts; c) fractal-like self-organization. Experimental investigation of the burst formation is presented. The microscopic analysis of growing, fractal-like structures is carried out, and a mechanism for such structure formation is suggested. It is supposed that fractal-like bacterial structures growth is based on the principle of successively forming multiple micro-bursts. A mathematical model has been suggested to reproduce the experimental results. The structures obtained by numerical modeling of population growth in the parameter space 'substrate concentration - bacterial movement rate' reproduce the corresponding experimental structures in the space 'nutrient concentration in the media - the density of the media'.