Performance of polymer-concrete composites in service life of maritime structures

University of Technology Sydney. Faculty of Engineering and Information Technology.Premature deterioration of Reinforced Concrete (RC) structures exposed to severe environment has become a global problem with serious economic consequences, environmental impact, and safety issues. According to the enormous investigations, it is evident that the dominant factor of this process is the chloride-induced corrosion of the steel reinforcement in RC structures. Diffusion of the chloride into the concrete occurs through the interconnected pores and surface cracks generated by different sources such as external loading and shrinkage. Large number of the wide cracks not only can accelerate the diffusion process but also enhance the probability of the steel corrosion leading to decreasing the service life of structures. In spite of many conducted studies, records and case studies confirm that the problem still exists. In this study, current significant corrosion preventing methods have been investigated and their advantages and disadvantages have been examined. Based on this investigation, modifying and improving the microstructure of the concrete, to reduce its permeability, gives the impression to be the most leading method due to easy implementation and lower cost. In the experimental program of this research two main research areas consisting (i) effect of polymer-concrete composites on mechanical properties of the concrete, and (ii) effect of polymer-concrete composites on service life of RC structures exposed to severe environmental exposure conditions have been investigated. In addition, two different categories of polymer-concrete composites including synthetic fibres and latex polymer have been selected to investigate their effects on mechanical properties and durability performance of the composites. According to the result of this study, polymer-concrete composites reveal enhancement on the mechanical properties of the concrete such as compressive strength, flexural strength, and tensile strength. Furthermore, to assess the durability performance of the polymer-concrete composites series of long-term tests (up to 720 days) have been conducted in the concrete laboratory of University of Technology Sydney. In this research, service life of the RC structure has been taken either as time of corrosion initiation (corrosion free service life) or time of cracking of the concrete cover due to steel corrosion (corrosion time). Chloride content measurement was utilized in this study to find the chloride diffusion rate in polymer-concrete composites exposed to high concentrated chloride solution for 24 months. Results of chloride content tests revealed that the polymer-concrete composites can significantly reduce the chloride diffusion rate in concrete and extend the corrosion-free service life of RC structures. To estimate the corresponding service life to corrosion time, an accelerated electrochemical method was deployed in order to obtain the results in relatively shorter time. The results of corrosion time also confirmed that the polymer-concrete composites can increase the service life of the structure considerably. Most of the previously proposed models available in the literature, consider the chloride diffusion coefficient as a constant parameter. In this study, a new mathematical model was proposed to determine the chloride diffusion coefficient as a time-dependent parameter. In the proposed model the effects of water cement ratio, cement type, cement content, and coarse aggregate proportion were investigated and included Finally, finite element analysis by Utilizing ABAQUS has been performed to verify the mathematical model. The results of the computer modeling and long-term experimental program are in reasonably good agreement

Nitric oxide radical scavenging potential of some Elburz medicinal plants

Some plants scavenge nitric oxide (NO) with high affinity. For this purpose, forty extracts from 26 medicinal plants, growing extensively in Elburz mountains, were evaluated for their NO scavenging activity. Total phenolic and flavonoid contents of these extracts were also measured by Folin Ciocalteu and AlCl3 colorimetric assays, respectively. Sambucus ebulus fruit aqueous extract and Pterocarya fraxinifolia leaf methanol extract showed better activity than others with IC50 equal to 29 and 65 g ml-1, respectively. NO is also implicated in inflammation and other pathological conditions, therefore very powerful scavenging activity of S. ebulus fruit extract may explain its very good anti-inflammatory activity. Phenolic and flavonoids contents of the extracts varied between 10.2 - 200.4 and 2.1 - 90.9 mg g-1 of extract, respectively. Good correlations could be found between total phenolic contents and NO scavenging activity through linear regression analysis (R2 = 0.63). There was also a better correlation between total flavonoids and NO scavenging activity (R2 = 0.73). High NO scavenging activity in plants can candidate them for testing their anti-inflammatory property.Key words: Antiinflammatory, flavonoid contents, medicinal plants, nitric oxide scavenging activity, phenolic contents, Sambucus ebulus, Pterocarya fraxinifolia

In vitro antioxidant and free radical scavenging activity of Leonurus cardiaca subsp. Persicus, Grammosciadium platycarpum and Onosma demawendicum

Antioxidant activity of the aerial parts of Leonurus cardiaca subsp. Persicus, Grammosciadium platycarpum and Onosma demawendicum were investigated employing six in vitro assay systems. IC50 for 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical-scavenging activity was in the order: O.demawendicum (221 ± 11.7) > L. cardiaca (144 ± 12.1) > G. platycarpum (45 ± 2.1) μgml-1, respectively. The extracts showed very good nitric oxide-scavenging and Fe2+ chelating ability activity. The L. cardiaca subsp. Persicus showed Fe2+ chelating ability activity as ethylenediaminetetraacetic acid (EDTA) (IC50 were 20 versus 18 μgml-1). None of the extracts exhibited good antioxidant activity in linoleic acid model. The extracts showed good reducing power that was better than vitamin C (p < 0.05). G. platycarpum and L. cardiaca subsp. Persicus had higher total phenolic and flavonoid contents than O. demawendicum. The total phenolic compounds in the extracts were determined as gallic acidequivalents, and total flavonoid contents were calculated as quercetin equivalents from a calibration curve.Keywords: Antioxidant activity, Fe2+ chelating, 1,1-diphenyl-2-picryl hydrazyl (DPPH), phenol, Leonurus cardiaca, Grammosciadium platycarpum, Onosma demawendicu

Antidepressant and antioxidant activities of Artemisia absinthium L. at flowering stage

Artemisia absinthium (Asteraceae) is widely used in Iranian traditional medicine. Its effects may be correlated with the presence of antioxidant compounds. Methanolic extract of A. absinthium aerial part at flowering stage was screened for antioxidant activities by five complementary test systems. Also, its antidepressant activity was determined by forced swimming (FST) and tail suspension tests (TST). The extract showed good antioxidant activity. Also, the extract showed good reducing power activitybetween 50 and 800 ìgml-1. The extract exhibited a good activity in H2O2 scavenging (IC50 = 243 ± 12.15 ìg ml-1). IC50 for iron ion chelating activity was 419 ± 20.95 ìg ml-1. Quercetin, BHA, EDTA and ascorbicacid used as positive controls in parallel experiments. The extract showed high phenolic and flavonoid contents. Extract showed good antidepressant activity in FST. The extract shortened remarkably the immobility period during the FST and TST and exhibited a dose dependent activity. All test groups were significantly different form control group (P 0.05) in TST. LD50 was 3700 mg/kg. These results introduced A. absinthium aerial parts as an easily accessible and edible source of natural antioxidants and antidepressant

Biological and pharmacological effects of Delphinium elbursense

Antidepressant, antihypoxic and antioxidant activities of aerial parts of Delphinium elbursense were investigated employing nine various assay systems. Antidepessant activity was examined by using forced swimming test and tail suspension test in mice. The extracts at all tested doses show significant activity as compared to control group. Antihypoxic activity was investigated in two models, haemic and circulatory. The effects were pronounced and dose-dependent in both model of hypoxia. Extracts showed weak antioxidant activity in some models. IC50 for 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical-scavenging activity was 116.2 ± 5.6 mg ml-1. Extracts showed nitric oxide-scavenging activity between 0.1 and 1.6 mg ml-1 (IC50 = 502.3 ± 18 mg ml-1) and a very weak Fe2+ chelating ability (IC50 = 1.01 ± 0.03 mg ml-1). It also exhibited low antioxidant activity in hemoglobin-induced peroxidation of linoleic acid but was capable of scavenging hydrogen peroxide in a concentration dependent manner. Extract show antihemolytic activity againts hydrogen peroxide (H2O2) induced hemolysis (558.7 ± 31 mg ml-1). The total phenolic compounds in extract were determined as gallic acid equivalents (52.24 ± 1.7) and total flavonoid contents were calculated as quercetin equivalents (17.26 ± 0.6) from a calibration curve.Keywords: Antidepressant, antihypoxic, Delphinium elbursense, flavonoid contents, forced swimming test, medicinal plants, phenolic contents, tail suspension testAfrican Journal of Biotechnology Vol. 9(34), pp. 5542-5549, 23 August, 201

Antioxidant, antibacterial, cytotoxic, and apoptotic activity of stem bark extracts of Cephalotaxus griffithii Hook. f

<p>Abstract</p> <p>Background</p> <p><it>Cephalotaxus </it>spp. are known to possess various therapeutic potentials. <it>Cephalotaxus griffithii</it>, however, has not been evaluated for its biological potential. The reason may be the remoteness and inaccessibility of the habitat where it is distributed. The main aim of this study was to: (1) evaluate multiple biological potentials of stem bark of <it>C. griffithii</it>, and (2) identify solvent extract of stem bark of <it>C. griffithii </it>to find the one with the highest specific biological activity.</p> <p>Methods</p> <p>Dried powder of stem bark of <it>C. griffithii </it>was exhaustively extracted serially by soaking in petroleum ether, acetone and methanol to fractionate the chemical constituents into individual fractions or extracts. The extracts were tested for total phenolic and flavonoid content, antioxidant (DPPH radical scavenging, superoxide radical scavenging, and reducing power models), antibacterial (disc diffusion assay on six bacterial strains), cytotoxic (MTT assay on HeLa cells), and apoptotic activity (fluorescence microscopy, DNA fragmentation assay, and flow cytometry on HeLa cells).</p> <p>Results</p> <p>Among the three extracts of stem bark of <it>C. griffithii</it>, the acetone extract contained the highest amount of total phenolics and flavonoids and showed maximum antioxidant, antibacterial, cytotoxic (IC₅₀of 35.5 ± 0.6 μg/ml; P < 0.05), and apoptotic (46.3 ± 3.6% sub-G0/G1 population; P < 0.05) activity, followed by the methanol and petroleum ether extracts. However, there was no significant difference observed in IC₅₀values (DPPH scavenging assay) of the acetone and methanol extracts and the positive control (ascorbic acid). In contrast, superoxide radical scavenging assay-based antioxidant activity (IC₅₀) of the acetone and methanol extracts was significantly lower than the positive control (P < 0.05). Correlation analysis suggested that phenolic and flavonoid content present in stem bark of <it>C. griffithii </it>extracts was responsible for the high antioxidant, cytotoxic, and apoptotic activity (P < 0.05).</p> <p>Conclusions</p> <p>Stem bark of <it>C. griffithii </it>has multiple biological effects. These results call for further chemical characterization of acetone extract of stem bark of <it>C. griffithii </it>for specific bioactivity.</p

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field