Chemical Structures of Adhesive and Interphase Parts in Sucrose/Citric Acid Type Adhesive Wood-Based Molding Derived from Japanese Cedar (Cryptomeria japonica)

In sucrose/citric acid based wood adhesive, the detailed bonding mechanism has still been unknown. Here, we investigated the detailed chemical structures of this adhesive wood (Japanese cedar)-based molding by using heteronuclear single quantum coherence–nuclear magnetic resonance (HSQC-NMR). NMR peaks associated with the furan-type structure appeared, suggesting that the furan compound was formed from sucrose and converted to a furan polymer during the adhesive process and that some of the furan structures in the polymers were ester-bonded with citric acid. The secondary forces between the furan polymers and wood components were thought to contribute to the adhesive effect. In our analysis of the interphase structure, primary hydroxyl groups of both polysaccharides and of lignin substructures were found to be esterified with citric acid. Additionally, some of the glycosidic bonds in polysaccharides were cleaved during the acidic condition produced by citric acid. The above results provided evidence of the polymerization of sucrose-derived 5-HMF, the esterification of wood components, and the degradation of polysaccharides during the molding process. Citric acid functioned as a clamp between the obtained furan polymer and the wood components. The sucrose/citric acid based wood adhesive can be defined as a hybrid-type wood adhesive, involving both secondary forces and chemical bonding interactions.

Ambient Climate Influences Anti-Adhesion between Biomimetic Structured Foil and Nanofibers

Due to their uniquely high surface-to-volume ratio, nanofibers are a desired material for various technical applications. However, this surface-to-volume ratio also makes processing difficult as van der Waals forces cause nanofibers to adhere to virtually any surface. The cribellate spider Uloborus plumipes represents a biomimetic paragon for this problem: these spiders integrate thousands of nanofibers into their adhesive capture threads. A comb on their hindmost legs, termed calamistrum, enables the spiders to process the nanofibers without adhering to them. This anti-adhesion is due to a rippled nanotopography on the calamistrum. Via laser-induced periodic surface structures (LIPSS), these nanostructures can be recreated on artificial surfaces, mimicking the non-stickiness of the calamistrum. In order to advance the technical implementation of these biomimetic structured foils, we investigated how climatic conditions influence the anti-adhesive performance of our surfaces. Although anti-adhesion worked well at low and high humidity, technical implementations should nevertheless be air-conditioned to regulate temperature: we observed no pronounced anti-adhesive effect at temperatures above 30 °C. This alteration between anti-adhesion and adhesion could be deployed as a temperature-sensitive switch, allowing to swap between sticking and not sticking to nanofibers. This would make handling even easier.

Sublimation of organic-rich comet analog materials and their relevance in fracture formation

Aims. The morphology of cometary nuclei is the result of an ongoing evolution and can provide valuable information to constrain the composition of comets. In our laboratory experiments we investigated the morphological evolution of comet analog materials, which consist of volatile, dust, and organic components. The laboratory results are aimed to help understand the evolution of cometary surfaces. Methods. We used spherical particles of fly ash and mixtures of ice, glycine, and sodium acetate as analog materials in different mass ratios to reproduce observed cometary morphologies. The cohesive and gravitational properties in the laboratory are scaled to cometary conditions to draw meaningful conclusions from the experimental results. The samples were placed in a vacuum sublimation chamber, cooled down to below 150 K, and were insolated with an external light source. To analyze the morphology of the samples, a camera was used to monitor the alterations of the surface. Results. Organic components in volatile-rich samples can have a distinct adhesive effect after the volatiles sublimate. During the sublimation process the sample volume decreases and fractures form on the sample surface. Due to the stability of the remaining volatile-depleted material, significant cliff collapses or ejected particles were not observed in the laboratory.

Effect of Sirolimus on Intra-Abdominal adhesion development in a rat model

Objective: Postoperative intraabdominal adhesions still cause significant morbidity in surgical patients. This study aims to evaluate the effects of an immunosuppressor known as Sirolimus and an antiadhesive membrane which is formed with sodium hyaluronate carboxymethylcellulose-based bioresorbable membrane (Seprafilm™) to the intraabdominal adhesion formation in a rat model. Materials and Methods: This experimental study was performed at an experimental research center, Yeditepe University Faculty of Medicine, Istanbul. Spraque-Dawley Rats, at a weight of about 250±20 gr, were used. Group 1 (n=8): Abdomen was closed after applying cecal abrasion (control group), group 2 (n=8): 10 x 30 mm Seprafilm™ was applied under the abdominal wall after cecal abrasion ( Seprafilm™ group ). Group 3 (n =8): Sirolimus (0,5 mg/kg) was applied (Sirolimus group). Adhesions quantitatively evaluated by a blinded assessor according to the classification of Nair and his colleagues. Results: Statistically significant difference in terms of adhesion severity scores according to the Nair classification was found between the Sirolimus and the control group (p=0,03). Whereas, no statistically significant difference was found between the Seprafilm™ and the control group (p=0,17). Similarly, no statistically significant difference was found between Seprafilm™ and sirolimus group (p=0,64). Conclusion: Although there was no statistically significant difference between intraperitoneal application of Sirolimus and Seprafilm™ group (p = 0.57), a statistically significant difference was found when each group compared with the control group (p=0,03). Combined anti-adhesive effect of Sirolimus and Seprafilm™ can be evaluated in future studies.

LOAD-BEARING CAPACITY OF THE FLANGE CONNECTION OF BEAMS, COVERING OF A SINGLE-STOREY INDUSTRIAL BUILDING TAKING INTO ACCOUNT ITS MUSHROOM SHAPE

The article deals with issues related to the analysis of steel frame structures. The subject of the study is the construction sector. The object of research is flanged joints of beams of coverings of one-storey industrial buildings. In order to achieve these goals, the following methods are used: analysis, synthesis, description, generalization and comparison. According to the results of the work, the features of forming the quality of interaction between flanged joints and high-strength bolts in the form of a nodal connection of coating beams are determined. Additionally, the analysis of features during the design work and production of flanged connections used for the implementation of popular design solutions for steel cross frames of single-storey buildings is carried out. The main directions of analysis of the state of steel structures in the presence of signs of deformation (mushroom shape) of the flange connection are disclosed. The obtained data helps to optimize the composition of structural reinforcement elements, as well as reduce the level of labor intensity in the production and installation of flange joints of single-storey buildings’ coating beams. In the course of the study, an experiment is conducted in which the principle of symmetry is used. The unidirectional connection in and between nodes is modeled using the elements considered. In this case, it is necessary to mention the phenomenon of the adhesive effect of the nodes during compression and the lack of adhesion during tension. The model takes into account the physical nonlinearity of the material properties, the behavior of which is set by bilinear dependencies under load

Effect of Lipopeptide-Loaded Chitosan Nanoparticles on Candida Albicans Adhesion and on the Growth of Leishmania Major

A strain B84 producing surfactin and bacillomycin D lipopeptides was identified as Bacillus amyloliquefaciens. B84 lipopeptides were extracted by acid precipitation, identified by mass spectrometry and loaded onto chitosan nanoparticles by ionotropic gelation process. The lipopeptide / chitosan nanoparticles have an average size of 569 nm, a zeta potential range of 38.8 mV and encapsulation efficiency (EE) of 85.58 %. The treatment of C. albicans cells with encapsulated lipopeptides showed an anti-adhesive activity of 81.17 % and a decreased effect of cell surface hydrophobicity « CSH » by 25.53%. An anti-leishmanial activity was also recorded with IC50 of 14.37 µg ml-1 and 22.45 µg mL-1 against L. major promastigote and amastigote forms, respectively. Cytotoxicity studies on human cells showed low cytotoxicity effect with HC50 value of 770 µg mL-1 towards human red blood cells and LC50 value of 234.56 µg mL-1 towards macrophage Raw 264.7 cell line. These lipopeptide / chitosan nanoparticles could be used as a potential delivery system of lipopeptides to improve both their anti-adhesive effect against C. albicans cells colonizing medical devices and their anti-infectious activity against leishmania.

Anti-Adhesive Effect of Porous Polylactide Film in Rats

Excessive adhesion between tissues on a significant area can cause the development of disorders, cosmetic problems, and ileus. Methods for preventing adhesion include the use of drugs and anti-adhesion barriers for physical blocking. In this study, the adhesion prevention effect of polylactide film in porous form was analyzed. A porous polylactide film was manufactured using a molecular weight of at least 100,000. To generate porosity, 98% methylene chloride and 95% ethyl alcohol were used as solvents. The thickness, surface, and internal pore shape of film were investigated. The crystal structures and melting temperature of film were measured. In the rat model, the presence and severity of adhesion were then analyzed. The thickness of the film ranged from 10 to 20 µm. The surface of the film contained pores with diameters of less than 10 µm. Partial crystallinity appeared from 15° to 20°, but the structure was amorphous overall. In the rat cecum abrasion model, adhesion occurred in 3 of the 13 rats in the polylactide experimental group, representing a 23.1% incidence rate. There were statistically significant differences in the severity of adhesion. The use of porous polylactide films can reduce the incidence of adhesion.