Poor Mechanical Resistance Research Articles

Physicochemical properties of esterified/crosslinked quinoa starches and their influence on bread quality.

Starch is the main component of quinoa seeds. However, quinoa starch has poor solubility in cold water and poor mechanical resistance and is easily aged, which limit its application. Therefore, modification of its structure to improve its functional properties is necessary. This research used acetic anhydride and sodium trimetaphosphate to modify the structure of starch molecules and investigated their influence on bread quality. The results showed that both esterification and crosslinking prevented the aggregation behavior of starch molecules. Moreover, they both decreased the gelatinization enthalpy change and relative crystallinity of the starch. Compared with native starch, modification significantly decreased the gelatinization temperature from 57.01 to 52.01 °C and the esterified starch exhibited the lowest enthalpy change with a 44.2% decrease. Modified starch increased the specific volume and decreased the hardness and chewiness of bread. Modification did not influence the moisture content in bread but impacted the water retention capacity, depending on the degree of modification. Low and medium degrees of modification improved the water retention capacity during storage. By contrast, a high degree of modification (10 g kg-1 crosslinking agent) decreased the water retention capacity. The dually modified quinoa starch (esterified and crosslinked) showed no influence on the textural properties of bread. This study demonstrated that both esterification and crosslinking significantly improved the functional properties of quinoa starch. Crosslinked or esterified quinoa starches have the potential to improve the textural properties of bakery products. © 2024 Society of Chemical Industry.

Pregled mogućnosti nadoknade kosti u cilju pretprotetske pripreme pacijenta

Introduction. The loss of the jaw bone, especially in the area of the alveolar process, can significantly complicate the procedure of prosthetic rehabilitation of prosthetic patients. The reason for the loss of the jaw bones are physiological and pathological processes. Materials. Bone replacements are widely used in the reconstruction of bone defects. The optimal characteristics of these materials are biocompatibility, bioinertness, biofunctionality and a special canalicular and intercanalicular system. Alloplastic bone replacements are inorganic, synthetic, biocompatible and bioactive bone replacements with osteoinductive potential. Hydroxyapatite is a preparation based on calcium phosphate. It has high biocompatibility, low immunogenicity and good osteoconductive characteristics. Poor properties are poor mechanical resistance as well as a low degree of resorption. Therefore, the research of chemically modified hydroxyapatites containing different ions was started. Conclusion. Calcium ions can be replaced by various metal ions like cobalt, aluminum, nickel, manganese, chromium, copper in a liquid medium.

Morphological and Mechanical Characterization of Extracellular Vesicles and Parent Human Synoviocytes under Physiological and Inflammatory Conditions.

The morphology of fibroblast-like synoviocytes (FLS) issued from the synovial fluid (SF) of patients suffering from osteoarthritis (OA), rheumatoid arthritis (RA), or from healthy subjects (H), as well as the ultrastructure and mechanical properties of the FLS-secreted extracellular vesicles (EV), were analyzed by confocal microscopy, transmission electron microscopy, atomic force microscopy, and tribological tests. EV released under healthy conditions were constituted of several lipid bilayers surrounding a viscous inner core. This "gel-in" vesicular structure ensured high mechanical resistance of single vesicles and good tribological properties of the lubricant. RA, and to a lesser extent OA, synovial vesicles had altered morphology, corresponding to a "gel-out" situation with vesicles surrounded by a viscous gel, poor mechanical resistance, and poor lubricating qualities. When subjected to inflammatory conditions, healthy cells developed phenotypes similar to that of RA samples, which reinforces the importance of inflammatory processes in the loss of lubricating properties of SF.

Biodegradable-Glass-Fiber Reinforced Hydrogel Composite with Enhanced Mechanical Performance and Cell Proliferation for Potential Cartilage Repair.

Polyvinyl alcohol (PVA) hydrogels are promising implants due to the similarity of their low-friction behavior to that of cartilage tissue, and also due to their non-cytotoxicity. However, their poor mechanical resistance and insufficient durability restricts their application in this area. With the development of biodegradable glass fibers (BGF), which show desirable mechanical performance and bioactivity for orthopedic engineering, we designed a novel PVA hydrogel composite reinforced with biodegradable glass fibers, intended for use in artificial cartilage repair with its excellent cytocompatibility and long-term mechanical stability. Using structure characterization and thermal properties analysis, we found hydrogen bonding occurred among PVA molecular networks as well as in the PVA–BGF interface, which explained the increase in crystallinity and glass transition temperature, and was the reason for the improved mechanical performance and better anti-fatigue behavior of the composites in comparison with PVA. The compressive strength and modulus for the PBGF-15 composite reached 3.05 and 3.97 MPa, respectively, equaling the mechanical properties of human articular cartilage. Moreover, the increase in BGF content was found to support the proliferation of chondrocytes in vitro, whilst the PVA hydrogel matrix was able to control the ion concentration by adjusting the ions released from the BGF. Therefore, this novel biodegradable-glass-fiber-reinforced hydrogel composite possesses excellent properties for cartilage repair with potential in medical application.

PENGARUH PENAMBAHAN SERAT RAMI DAN BATANG PISANG TERHADAP KEKUATAN IMPAK DAN FLEKSURAL BASIS GIGI TIRUAN AKRILIK

Introduction : Acrylic denture in its use often results in fractures and one of the causes is due to poor mechanical resistance, especially to impact strength. Several methods to prevent broken acrylic, include the addition of fibers that function as reinforcement. There are 2 types of fibers, synthetic and natural fibers. Synthetic fibers are relatively expensive, so an alternative is needed, namely the use of natural fibers (Ramie and banana stem). This study purposed to determine the effect of adding ramie fiber and banana stem to impact and flexural strength of acrylic denture base. Methods : Experimental Laboratory, number of 60 samples consisted of 30 samples for flexural and impact tests. The sample was an acrylic plate; size 65x10x2.5 mm for Flexural Test and 80x10x4 mm (Flatwise impact method without notched) for Impact Test. The fiber concentration added was 1.6% of the sample weight. The sample consisted of 3 groups, namely control, the addition of ramie and banana stem fibers. Flexural test with UTM and Impact test with Charpy method. Results : Flexural and impact strength mean value of the ramie fiber group had the highest value (132.7459MPa; 7.9859 x 10-3Joule/mm2), followed by the control group (99.8499MPa; 4.2757 x 10-3Joule/mm2) and smallest value was in banana midrib fiber group (91.6865MPa; 3.0303 x 10-3Joule/mm2). The LSD test of significance(p) between each group in flexural and Impact Strength tests showed a significant difference (p<0.05). Pearson correlation test showed a significant positive correlation between the two tests. Conclusion : The addition of ramie fiber can increase the impact and flexural strength of denture acrylic, but it is different from the addition of banana midrib fiber because the presence of flavonoids (phenol compounds) it contains causes a decrease in the strength of denture acrylic.

Cross-Linked Enzyme-Adhered Nanoparticles (CLEANs) for Continuous-Flow Bioproduction.

Nanostructured but micro-sized biocatalysts were created by bottom-up technology using multi-functionalized silica nanoparticles (NPs) as nano-sized building blocks to form cross-linked enzyme-adhered nanoparticles (CLEANs) as robust micro-sized particles with beneficial internal structure and good mechanical properties. Systematic surface modification of NPs with a grafting mixture consisting of organosilanes with reactive (aminopropyl) and inert (e. g., vinyl, propyl, phenyl, or octyl) functions resulted in functional NPs enabling cross-linking agents, such as glutardialdehyde or bisepoxides (glycerol diglycidyl ether, neopentylglycol diglycidyl ether, and poly(propylene glycol) diglycidyl ether), to bind and cross-link enzymes covalently and to form macroporous microparticles. These CLEANs were able to diminish several weaknesses of traditional cross-linked enzyme aggregates as biocatalysts, such as poor mechanical resistance, difficult recovery, and storage, strengthening their use for packed-bed enzyme reactors. Lipase B from Candida antarctica (CaLB) was selected as model enzyme for development of robust CLEANs, which were successfully tested for various industrially relevant applications including a kinetic resolution of a racemic alcohol and the production of various natural fragrance compounds under continuous-flow conditions.

Osteosynthesis devices in absorbable Magnesium alloy in comparison to standard ones: a Systematic Review on effectiveness and safety.

Background and aim of the work:Magnesium (Mg) is a metal physiologically present in bone tissue and essential for bone health. Mg-based alloys exhibit mechanical properties, namely density and strength, similar to human cortical bone. These features have been exploited for the development of osteosynthesis devices in biodegradable Mg-based alloys. Accordingly, the aim of this study is to rank the effectiveness and safety of Mg-based alloys applied in bone surgery in comparison to other suitable metals, focusing in particular on Mg superior biocompatibility and biodegradability.Methods:a systematic review of the literature was conducted including only primary research studies dealing with patients suffering from fractured or osteotomized bones fixed using Mg-based osteosynthesis devices.Results:literature revision suggested Mg-alloys holding comparable properties and side effects in comparison with titanium (Ti) screws, thus showing similar efficacy and safety. Particularly, the gas formation in the carpal bones was identified as the main side effect of the Mg-alloys, during the corrosion/degradation phase of Mg.Conclusions:according to the literature, the main advantages exploiting Mg-alloys for bone implants are related to their biocompatibility, bio-absorbability/-degradability, the lack of surgical removal, osteoconductivity and antibacterial activity. On the opposite, the main limitation of Mg-alloys is due to the poor mechanical resistance of small devices that lack of sufficient strength to withstand high forces. Therefore, an important future prospect could rely in the development of innovative hybrid systems aimed at fixing high load-bearing fractures, as well as in regenerative medicine by developing new Mg-based engineered scaffolds. (www.actabiomedica.it)

Industrial applications of superhydrophobic coatings: Challenges and prospects

The use of the superhydrophobic coatings and materials in industry is not satisfactory after the intensive activity in research laboratories in the last two decades. We discussed the reasons for this adverse situation under several topics in this review article. The most important issues are the insufficient mechanical resistance and inevitable contamination of the SH surfaces under outdoor conditions, resulting in short useful life-time. The fabrication of a SH surface requires a rough structure with tiny textures on it and this frail framework has a poor mechanical resistance. The topics of superfluous production of small scale and expensive SH surfaces, the difficulty to obtain transparent and also self-healing SH surfaces, the inefficient anti-icing applications of the SH coatings are also discussed.

Biomaterials preparation by electrospinning of gelatin and sodium hyaluronate/gelatin nanofibers with non-toxic solvents

Gelatin (Ge) based fibers have been produced by electrospinning with a non-toxic solvent for preparing membranes usable in maxillofacial surgery. Ge and Ge/sodium hyaluronate (SH) nanofibers were successfully electrospun to produce membranes whose thickness was around 150 to 200μm. The mean fiber diameter reached a maximum of 660nm for Ge fibers and 210nm for Ge/SH fibers. The presence of Ge and SH was confirmed in the membranes by Raman spectroscopy. Ge membranes had low mechanical properties and only small samples of 0.5cm in size could be retrieved from the collector as larger sample tended to tear and break. Ge/SH membranes could be retrieved from the collector slightly easily. Membranes could be handled carefully but in vivo implantation could not be planned due to poor mechanical resistance. Crosslinking by glutaraldehyde vapors reduced the mean porosity of Ge membranes; it totally prevents membranes to be retrieved from the collector. Beta tricalcium phosphate (β-TCP) particles were added with Ge during electrospinning to increase osseointegration of the membranes and promote bone formation. β-TCP particles formed agglomerates outside the fibers, and we could not obtain β-TCP particles inside the Ge fibers due to their low diameter. In general, electrospun membranes lacked reproducibility. Despite the great interest of Ge-based membranes and Ge/β-TCP membranes, the low mechanical properties of the fibers, the lack of reproducibility and the difficulty to retrieve the membranes from the collector did not allow our biomaterials to be implanted or to be envisaged for industrial production.

Robust superhydrophobic SiO2/polydimethylsiloxane films coated on mild steel for corrosion protection

One of the biggest obstacles for superhydrophobic films in applications is their poor mechanical resistance. In this research, robust superhydrophobic SiO2 films were constructed on mild steel (MS) for corrosion protection by the combination of rough electrodeposited SiO2 (E-SiO2) films and durable polydimethylsiloxane (PDMS) polymer with low surface energy. Results show that the PDMS content has a great effect on the microtopography, wettability, roughness, and wear-resistance of the final films. EIS measurements indicate that as-prepared robust superhydrophobic E-SiO2/PDMS films exhibit good corrosion inhibition efficiency of up to 99.99 % for MS substrates in 3.5 wt.% NaCl solution.

Polydopamine deposition with anodic oxidation for better connective tissue attachment to transmucosal implants.

Nowadays, most designs for the transmucosal surface of implants are machined-smooth. However, connective tissue adhered to the smooth surface of an implant has poor mechanical resistance, which can render separation of tissue from the implant interface and induce epithelial downgrowth. Modification of the transmucosal surface of implants, which can help form a good seal of connective tissue, is therefore desired. We hypothesized that anodic oxidation (AO) and polydopamine (PD) deposition could be used to enhance the attachment between an implant and peri-implant connective tissue. We tested this hypothesis in the mandibles of Beagle dogs. AO and PD were used to modify the transmucosal region of transmucosal implants (implant neck). The surface microstructure, surface roughness and elemental composition were investigated in vitro. L929 mouse fibroblasts were cultured to test the effect of PD on cell adhesion. Six Beagle dogs were used for the in vivo experiment (n=6 dogs per group). Three months after building the edentulous animal model, four groups of implants (control, AO, PD and AO + PD) were inserted. After 4months of healing, samples were harvested for histometric analyses. The surfaces of anodized implant necks were overlaid with densely distributed pores, 2-7μm in size. On the PD-modified surfaces, N1s, the chemical bond of nitrogen in PD, was detected using X-ray photoelectron spectroscopy. L929 developed pseudopods more quickly on the PD-modified surfaces than on the surfaces of the control group. The in vivo experiment showed a longer connective tissue seal and a more coronally located peri-implant soft-tissue attachment in the AO + PD group than in the control group (P<.05). The modification of AO + PD on the implant neck yielded better attachment between the implant and peri-implant connective tissue.

A study of CO2 capture by high initial strength Portland cement pastes at early curing stages by new non-conventional thermogravimetry and non-conventional differential thermal analysis

Although the literature presents intensive studies based on monitoring cement hydration in adiabatic and semi-adiabatic environments, such as non-conventional differential thermal analysis (NCDTA) systems, studies of cement hydration in controlled climatic chambers are very rare. Using three W/C ratios (0.5, 0.6 and 0.7) and three relative humidity conditions (60, 80 and 100%) at 25 °C, the authors analyzed in real time the evolution of cement hydration reaction during the first 24 h in an environmental-controlled chamber. The main objective of this paper is to present two new developed systems of NCDTA (NNCDTA) and non-conventional TG and to show, using high-strength sulfate-resistant Portland cement pastes in a controlled chamber as application examples, how the developed systems measure on real time the thermal effects and the mass changes that occur during hydration and carbonation reactions. The captured CO2 mass can be quantified as it occurs by carbonation curves. The results are in agreement with the mechanical and structural properties of the used pastes and with their TG/DTG data, after being processed by different operational conditions. Carbonation for 24 h alters significantly the cement hydrated paste composition, resulting in final poor mechanical resistance properties. However, carbonation for 1 h, in specific conditions, enhances them when compared to a non-carbonated reference paste, due to a final higher content of silica and alumina hydrated phases and to a lower mass ratio between that of their combined water and their total mass as well.

Attrition Study of Cement-Supported Biomass-Activated Calcium Sorbents for CO2 Capture

An enhanced CO2 capacity was reported recently for biomass-modified Ca-based sorbent, but undesired attrition resistance was also observed. In this study, cement was used as a support for biomass-activated calcium sorbent during the granulation process to improve the poor mechanical resistance. Attrition tests were carried out in an apparatus focused on impact breakage to evaluate how the biomass addition and cement support influence the particle strength during Ca looping. The results showed that biomass addition impairs the mechanical strength and that a cement support can improve it, as reflected in the breakage probability and size change after impact of pellets that had experienced calcination and multiple calcination/carbonation cycles. Larger-sized particles suffered more intense attrition. The mechanical strength of the sorbents declined significantly after higher-temperature calcination but increased after carbonation. After multiple cycles, the mechanical strength of particles was greatly enhanc...

Influence of low contents of superhydrophilic MWCNT on the properties and cell viability of electrospun poly (butylene adipate-co-terephthalate) fibers

The use of poly (butylene adipate-co-terephthalate) (PBAT) in tissue engineering, more specifically in bone regeneration, has been underexplored to date due to its poor mechanical resistance. In order to overcome this drawback, this investigation presents an approach into the preparation of electrospun nanocomposite fibers from PBAT and low contents of superhydrophilic multi-walled carbon nanotubes (sMWCNT) (0.1–0.5wt.%) as reinforcing agent. We employed a wide range of characterization techniques to evaluate the properties of the resulting electrospun nanocomposites, including Field Emission Scanning Electronic Microscopy (FE-SEM), Transmission Electronic Microscopy (TEM), tensile tests, contact angle measurements (CA) and biological assays. FE-SEM micrographs showed that while the addition of sMWCNT increased the presence of beads on the electrospun fibers' surfaces, the increase of the neat charge density due to their presence reduced the fibers' average diameter. The tensile test results pointed that sMWCNT acted as reinforcement in the PBAT electrospun matrix, enhancing its tensile strength (from 1.3 to 3.6MPa with addition of 0.5wt.% of sMWCNT) and leading to stiffer materials (lower elongation at break). An evaluation using MG63 cells revealed cell attachment into the biomaterials and that all samples were viable for biomedical applications, once no cytotoxic effect was observed. MG-63 cells osteogenic differentiation, measured by ALP activity, showed that mineralized nodules formation was increased in PBAT/0.5%CNTs when compared to control group (cells). This investigation demonstrated a feasible novel approach for producing electrospun nanocomposites from PBAT and sMWCNT with enhanced mechanical properties and adequate cell viability levels, which allows for a wide range of biomedical applications for these materials.

Effect of homogenization conditions on properties of gelatin–olive oil composite films

Gelatin–olive oil composite films were prepared through emulsification to improve water barrier ability of gelatin-based films. The effects of homogenization conditions of film-forming dispersions (FFD) on lipid droplets distributions in the FFD and films were evaluated and compared. Some selected physical properties, e.g., water vapor permeability (WVP), microstructure of the films were also evaluated. The rotor–stator homogenizer provided a lower energy input and so the largest particles were observed in the related FFD and films. These films exhibited excellent water barrier ability, but poor mechanical resistance, extensibility and transparency. The microfluidizer provided the FFD with lower and narrower particle size distributions, promoting mechanical resistance, extensibility and transparency of the films. The physical properties of the emulsified films were dependent on the special microfluidization pressure or cycle used, e.g., the WVP of the films decreased upon increasing microfluidization pressure or cycle. The present results indicated that the microfluidizer can be used to modulate lipid droplets in the FFD, thus films’ properties.

Transglutaminase Crosslinked Pectin- and Chitosan-based Edible Films: A Review

The production of biodegradable and edible films with desired mechanical characteristics and gas barrier properties represents one of the most advanced challenges in the field of food wrapping and coating. New edible films can serve not only to provide food with physical protection but also to reduce loss of their moisture, to restrict absorption of oxygen, to lessen migration of lipids, to improve their mechanical handling features, and as materials, to apply in direct contact with internal food to realize a multilayer food packaging. Polymers derived from natural products, like carbohydrates and proteins, offer the greatest opportunities as component of edible films since their biodegradability and environmental compatibility are assured and they can also supplement the nutritional value of specific foods. However, excessive water solubility and poor water vapor barrier properties, and often poor mechanical resistance, have their application limited until the present time. Numerous studies have been carried out to improve their properties by preparing composite and multi-component films or by physically and chemically crosslinking their natural components. In the present review we summarize the main results obtained by crosslinking with the enzyme transglutaminase different proteins contained in multi-component pectin- and chitosan-based edible films, having the aim to create environmentally-friendly “bioplastics” with mechanical and permeability properties similar to the ones exhibited by plastics of petrochemical origin.

Microtribological rating of transparent conducting oxide for thin film solar cells

In this study, the mechanical properties of transparent conducting oxide (TCO) deposited on glass substrates, namely, aluminium doped zinc oxide (ZnO:Al) and fluorine doped tin oxide (SnO2:F) for the application of amorphous or amorphous/microcrystalline silicon solar cells, were investigated. The ZnO : Al thin films were deposited by either inline reactive ac magnetron sputtering or radio frequency magnetron sputtering utilising ceramic targets. The SnO2:F thin films were prepared using either inline or offline chemical vapour deposition (CVD). The micromechanical properties such as elastic and permanent deformation, microtribological properties and scratch resistance were measured to assess the film properties. The micro-structure-analysis method (MISTAN) was used to characterise those properties in situ with high local resolution. The inline reactive ac magnetron sputtered ZnO:Al films show relatively good scratch resistance. The surface structure of ZnO:Al films can be roughened by an etching process in order to enhance the scattered light into the cells. At the same time, the microfriction of the ZnO:Al films under the same load is higher after the etching process. Also the elastic and permanent deformation of inline reactive ac magnetron sputtered ZnO:Al films are increased after etching. The etching process has a significant impact on the radio frequency magnetron with ceramic targets deposited ZnO:Al films, since the scratch resistance of these films can be significantly improved by the etching process. The results show that the SnO2:F films possess poor mechanical resistance and planar surface structure.

Electrochemical oxygen sensors for on-line monitoring in lead–bismuth alloys: status of development

This paper presents the state of development of oxygen sensors based on the electromotive force (emf) measurement at null current, using yttria stabilized zirconia as solid electrolyte for application in liquid lead–bismuth eutectic (LBE), which is envisaged as a nuclear coolant or as a spallation target in accelerator driven system (ADS) for nuclear waste transmutation. The assembly procedure, the calibration method, as well as the summary of the various validation tests undergone in both static and loop facilities are presented so as to define a real state of achievement and the basics needs for further studies. The sensors are efficient, accurate, rapid and reliable for research loops. However, the poor mechanical resistance as well as the effect of traces of impurities, promoting an increasing time-drift under certain conditions, are to be further studied to improve the sensor reliability for a nuclear use. The oxygen and chromium solubilities were reassessed in the process of the sensor testing, those relations are also given and discussed.

Polyacrylic gel beads reinforced by a polyamide membrane: application to copper removal in aqueous media

Polyacrylic acid gel is known for its ion chelating properties. Its poor mechanical resistance hinders its use in extraction operations. Crosslinking can improve the mechanical resistance but lowers the chelating capacity. A gel encapsulation technique has been developed to obtain a material constituted by a low cross linked polyacrylic gel coated by a polyamide membrane and having improved mechanical resistance with respect to the corresponding gel. Extracting properties of various metal ions (Cu, Ni, Co and Zn) carried out in “batch” and “column” processes are presented. Mass transfer modeling studies have been carried out by using the mass action law for the ion exchange equilibrium and by describing the ion flow with the Nernst—Planck equation. Collocation in finite elements was used to solve the model equations. Results indicate that the capsules can be compared with ion exchange resins.

Quality evaluation of foodstuffs frozen in a cryomechanical freezer

Cryomechanical freezing is recommended for delicate products, with poor mechanical resistance (shrimps, raspberries, strawberries) or those that change their appearance during freezing (chicken, mushrooms, shrimps). The aim of this work is to study the quality aspects related to the application of cryomechanical freezing compared to the use of a conventional mechanical freezer. In order to determine whether or not the use of the combined freezer provokes an improvement in the quality of the final product, different kinds of foodstuffs were chosen and analysed before and after freezing by both methods. The selected products were: chicken escallops, hamburgers, strawberries, asparagus and mushrooms. The quality parameters analysed for this purpose were: drip loss during thawing, texture and colour. The variation in mechanical resistance was also evaluated as a function of the immersion time to determine the hardness of the protective crust formed by the liquid N 2 pretreatment.