The study investigates the application of waste rubber in cement-stabilized base course (CBC), aiming to address internal stresses, reflective cracks, and waste disposal issues. Mixtures of gravel ...and sand stabilized with varying cement and rubber content were examined, including reference mixtures and those with granulated rubber or rubber threads, a total of 17 mixtures. Mechanical properties, durability, and environmental impact were evaluated through standard tests such as Proctor elements, compressive and tensile strengths, freezethaw resistance, shrinkage, and scanning electron microscope analysis. Non-standard, non-contact methods like ultrasonic pulse velocity and 3D digital image correlation were employed. Results indicate the feasibility of using waste rubber in CBC, with the optimal mixture containing 5 % cement and 20 % rubber as a replacement for sand showing satisfactory compressive strength (3.01 MPa) for application as a base layer, reduced stiffness, improved frost resistance (9.76 %), improved tensile to compressive strength ratio (52.99 %), and increased resistance to reflective cracking comparing to reference mixture. Moreover, it exhibited minimal shrinkage compared to other mixtures. The study underscores the importance of assessing environmental acceptability in waste materials for road construction, emphasizing the need for further research. Furthermore, the possibility of employing non-contact testing methods has been demonstrated.
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•The optimal composition of rubberized CBC has been defined.•Rubber improves freeze – thaw resistance of CBC.•Rubber decreases the shrinkage of CBC.•The use of rubber in CBC does not pose an environmental risk.
The aim of this research was to test the antibacterial activity of Pinus pinaster aqueous bark extract (PABE) and its basic components against multidrug-resistant isolates of Acinetobacter baumannii ...belonging to European clone I and II, isolated previously from the clinical outbreaks. The minimum bactericidal concentration of PABE against both clones of A. baumannii was 200 mg ml.sup.-1, while lower concentrations showed high antibacterial activity. After 24 h of treatment with 100, 50 or 10 mg ml.sup.-1 of extract, the reduction in the number of A. baumannii isolates belonging to European clone I and II was 85.8 + or - 2.5 %, 78.5 + or - 1.1 %, 66.3 + or - 2.5 % and 90.2 + or - 1.7 %, 78.6 + or - 1.2 %, 69.8 + or - 0.7 %, respectively. Several basic components: caffeic acid, catechin, epicatechin, gallic acid and vanillin, detected in the extract by high performance liquid chromatography, contributed to the antibacterial activity of the extract against both clones of A. baumannii. However, the antibacterial activity of extract was higher than that of each tested basic component suggesting that proanthocyanidins, which were present in quite a large amount in the extract, might have also contributed to the activity of the extract. Antibacterial activity of PABE against A. baumannii reveals that complex and inexpensive natural product might be useful in combat against naturally competent bacteria that easily acquire resistance against antibiotics. Keywords: antimicrobials, aqueous extract, bacteria, multidrug-resistant pathogens, natural compounds
Aim
To evaluate, in vitro antimicrobial ability of two probiotic toothpastes (one containing Lactobacillus paracasei, other containing Lactobacillus acidophilus) and one toothpaste without probiotic ...separately, and in a combination with two different mouthrinses (one containing essential oils and the other containing hexitidine).
Methods
Antimicrobial susceptibility was checked by using the ditch method and Clinical Laboratory Standard Institute (CLSI)
guidelines. Two different toothpastes with probiotic, toothpaste without probiotic and two different mouthrinses were tested against the following selected microorganisms: Candida albicans, Candida tropicalis, Enterococcus faecalis, Streptococcus salivarius and Staphylococcus aureus. Kruskal-Wallis test and MannWhitney U test were used for the statistical analysis (p≤ 0.05).
Results
Probiotic toothpastes had better inhibitory effect than toothpaste without probiotic in the case of Candida albicans
(p=0.043) and Streptococcus salivarius (p=0.043). In all cases, toothpastes had stronger inhibition capacity than mouthrinses
(p≤0.05).
Conclusion
Probiotic toothpastes, as a relatively new concept in the prevention of oral infectious diseases such as caries and periodontal disease, can contribute to the prevention of oral infectious diseases.
We analyze the stellar age indicators (Dn4000 and EW(Hδ)) and sizes of 467 quiescent galaxies with M* ≥ 1010 M at z ∼ 0.7 drawn from DR2 of the LEGA-C survey. Interpreting index variations in terms ...of equivalent single stellar population age, we find that the median stellar population is younger for larger galaxies at fixed stellar mass. The effect is significant, yet small; the ages of the larger and smaller subsets differ by only <500 Myr, much less than the age variation among individual galaxies (∼1.5 Gyr). At the same time, post-starburst galaxies-those that experienced recent and rapid quenching events-are much smaller than expected based on the global correlation between age and size of normal quiescent galaxies. These coexisting trends unify seemingly contradictory results in the literature; the complex correlations between size and age indicators revealed by our large sample of galaxies with high-quality spectra suggest that there are multiple evolutionary pathways to quiescence. Regardless of the specific physical mechanisms responsible for the cessation of star formation in massive galaxies, the large scatter in Dn4000 and EW(Hδ) immediately implies that galaxies follow a large variety of evolutionary pathways. On the one hand, we see evidence for a process that slowly shuts off star formation and transforms star-forming galaxies to quiescent galaxies without necessarily changing their structures. On the other hand, there is likely a mechanism that rapidly quenches galaxies, an event that coincides with dramatic structural changes, producing post-starburst galaxies that can be smaller than their progenitors.
Antimicrobial peptides often show broad-spectrum activity due to a mechanism based on bacterial membrane disruption, which also reduces development of permanent resistance, a desirable characteristic ...in view of the escalating multidrug resistance problem. Host cell toxicity however requires design of artificial variants of natural AMPs to increase selectivity and reduce side effects. Kiadins were designed using rules obtained from natural peptides active against E. coli and a validated computational algorithm based on a training set of such peptides, followed by rational conformational alterations. In vitro activity, tested against ESKAPE strains (ATCC and clinical isolates), revealed a varied activity spectrum and cytotoxicity that only in part correlated with conformational flexibility. Peptides with a higher proportion of Gly were generally less potent and caused less bacterial membrane alteration, as observed by flow cytometry and AFM, which correlate to structural characteristics as observed by circular dichroism spectroscopy and predicted by molecular dynamics calculations.
Digital image correlation (DIC) is a method of point displacement measurement by an optical system. If two cameras are used for capturing the same point displacement, three-dimensional data are ...obtained using the 3D-DIC method. The areas of application of this method in pavement construction are diverse, but it is mainly used for displacement monitoring during standard tests of the failure of specimens due to load application. Furthermore, DIC technology was used only for testing particular material characteristics and assuming their influence on the overall pavement system. Within this research, DIC was applied in two areas: defining material mechanical characteristics and analyses of pavement structure behaviour under cyclic loading. The scope of this research was to gain more insights into DIC’s potential application within pavement behaviour analyses, specifically on cement-bound granular material (CBGM) characterisation. Results from this study confirm the suitability of 3D-DIC technology for pavement material characterisation. Furthermore, it is shown that certain trends of material behaviour defined on the simple material level of each independent pavement layer will significantly differ when it is placed in the system, and this kind of complex analysis is possible by using 3D-DIC technology.
A new type of low-strength concrete made with steel slag and gravel was investigated in this report. Increasing the amount of cement or steel slag in the mix increased the maximum dry density and ...optimum moisture content of the concrete. Additionally, the compressive and indirect tensile strength of the concrete increased with curing age. The strength of mixes with low cement contents increased with the slag content, while that of mixes with higher cement contents decreased with slag content. Finally, the average indirect tensile strength for all mixes as a percentage of compressive strength was ∼14%.
The high stiffness of cement-bound aggregate (CBA) is recognized as its main drawback. The stiffness is described by the modulus of elasticity, which is difficult to determine precisely in CBA. ...Incorporating rubber in these mixtures reduces their stiffness, but mathematical models of the influence of rubber on the mechanical characteristics have not previously been defined. The scope of this research was to define a prediction model for the compressive strength (fc), dynamic modulus of elasticity (Edyn) and static modulus of elasticity (Est) based on the measured ultrasonic pulse velocity as a non-destructive test method. The difference between these two modules is based on the measurement method. Within this research, the cement and waste rubber content were varied, and the mechanical properties were determined for three curing periods. The Edyn was measured using the ultrasonic pulse velocity (UPV), while the Est was determined using three-dimensional digital image correlation (3D DIC). The influence of the amount of cement and rubber and the curing period on the UPV was determined. The development of prediction models for estimating the fc and Est of CBA modified with waste rubber based on the non-destructive test results is highlighted as the most significant contribution of this work. The curing period was statistically significant for the prediction of the Est, which points to the development of CBA elastic properties through different stages during the cement-hydration process. By contrast, the curing period was not statistically significant when estimating the fc, resulting in a simplified, practical and usable prediction model.
The aim of this research was to better understand the influence of adding waste rubber in cement bound aggregate (CBA) by testing both the unconfined and triaxial stress state. CBA with waste rubber ...was tested in this manner aiming to analyse influence of the confining pressure on the material behaviour. The results indicate that adding 20% rubber to a high cement content mix can assimilate the high stiffness caused by the high cement paste content, resulting in a mixture with increased cement paste content to facilitate in situ compaction. Additionally, a low confining pressure of 40 kPa has the most impact on the elastic properties/stiffness and it would be more appropriate to measure the CBA elasticity modulus with moderate lateral (confining) pressure. Finally, the practical implication of this research is that, in pavement mechanistic-empirical design, a correction of the measured uniaxial static modulus of elasticity by 10-15% should be adopted.
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