Calamus deerratus fibre reinforced natural rubber vulcanizates

This research study investigates the potentials of Calamus deerratus fibre (CDF) as a reinforcing filler in natural rubber, Standard Nigerian Rubber (SNR10)   vulcanizates. The Calamus deerratus was cut, dried, pulverized, characterized and incorporated into the natural rubber compounds and the effects on the cure  characteristics and physico-mechanical properties of the CDF-reinforced natural rubber vulcanizates were determined. The results of the analyses, in comparison with a standard carbon black, CB(N330)-filled vulcanizates showed that the CDF manifested a reinforcing effect on the SNR10 vulcanizates but inferior to carbon black, N330-filled vulcanizates. The maximum torque, abrasion resistance, modulus, specific gravity and hardness increased while the scorch time, cure time,   elongation at break and rebound resilience decreased with increasing filler content. The cure time and scorch time were however higher in CDF-filled SNR10   vulcanizates compared to those filled with carbon black, N330. Tensile strengths of CB(N330)- and CDF- filled vulcanizates increased to optimum levels at 40 phr  and 30 phr respectively and decreased with increasing filler content. The results however showed that CDF imparted lower reinforcing potential as shown by the   lower tensile strength, abrasion resistance and modulus. The hardness results of the CDF-filled vulcanizates showed slight superiority over that of CB(N330)-filled vulcanizates.Keywords: Natural rubber, Calamus deerratus, fillers, reinforcement and vulcanizates

The reinforcing potentials of Velvet tamarind seed shell as filler in natural rubber compounds

This work focused on the development of a reinforcing filler from renewable natural plant resources as part of the ongoing search for environmental friendly fillers that will substitute synthetic reinforcing fillers such as carbon black and silica in rubber manufacturing. The cure characteristics, physico-mechanical and equilibrium swelling properties of natural rubber, Standard Nigerian Rubber (SNR10) vulcanizates separately filled with commercial grade carbon black (CB), N330 and pulverized natural plant material, Velvet tamarind (VT), seed shell were investigated. The results of the analyses showed that the scorch and cure times decreased while the maximum torques increased with increasing filler loading for both filled-SNR10 vulcanizates. The tensile strengths of both VT-filled and CB (N330) filled-SNR10 vulcanizates increased to 30 phr and 40 phr respectively and decreased with increasing filler loading. The modulus at 100% strain, specific gravity, abrasion resistance and hardness increased while elongation at break, equilibrium swelling and rebound resilience decreased with increasing filler loading for both filled-SNR10 vulcanizates. The results showed that Velvet tamarind seed shell manifested a reinforcing effect on the SNR10 compounds but lower than that of CB (N330) filler.Keywords: Natural rubber, fillers, reinforcement and vulcanizate properties

Physicochemical Characteristics and Levels of Some Heavy Metals in Soils around Metal Scrap Dumps in Some Parts of Delta State, Nigeria

Some physicochemical characteristics and heavy metal levels in soil samples around metal scrap dumps at Abraka and Agbor vicinities of Delta State, Nigeria, were analysed in order to assess the effects of the dumps on the soils. Conventional analytical methods were employed for the determination of these physicochemical parameters while heavy metals in the soil samples where analysed using Atomic Absorption Spectrophotometer. The results of the physicochemical analysis showed that the pH values in all the sites ranged from 7.01 to 7.99 indicating neutrality to slight alkalinity of the soils. The Total Organic Carbon values ranged from 0.38 to 0.54% indicating presence of some organic matter and some microbiological activities in the soil samples. The high conductivity values ranging from 165 to 201μs/cm indicated significant presence of some soluble inorganic salts in soils studied. For all the physicochemical values recorded, the soil samples at Agbor had slightly higher values than those of Abraka. The heavy metal levels for the soils in Abraka and Agbor respectively were (mgkg-1) 1.50 and 1.52 for Cd, 5.10 and 4.48 for Ni, 1431 and 1411 for Fe, 74.26 and 97.21 for Zn, 14.31 and 34.21 for Cu, 24.0 and 18 for Cr, 9.73 and 10.54 for Co, and then 12.24 and 14.47 for Pb. The levels were all higher than those recorded in the control sites. A consistent trend showing a decrease in the concentration of heavy metals was observed for soil samples at increased distances from the impact points for the two towns studied. Metal was observed for soil samples at increased distances from the impact point for the two towns studied. The results from the contamination index indicated a significant degree of soil contamination for Pd, Cd, Co, Cu and Zn in the soils studied showing a higher degree of contamination for these metals. These soils therefore constitute a major health risk to the local population. This study successfully related and attributed the presence of heavy metals with anomalous concentration in the soils to anthropogenic inputs from the metal scrap dumps. @JASEM.J. Appl. Sci. Environ. Manage. December, 2010, Vol. 14 (4) 57 - 6

Reactive oxygen species via redox signaling to PI3K/AKT pathway contribute to the malignant growth of 4-hydroxy estradiol-transformed mammary epithelial cells.

The purpose of this study was to investigate the effects of 17-β-estradiol (E2)-induced reactive oxygen species (ROS) on the induction of mammary tumorigenesis. We found that ROS-induced by repeated exposures to 4-hydroxy-estradiol (4-OH-E2), a predominant catechol metabolite of E2, caused transformation of normal human mammary epithelial MCF-10A cells with malignant growth in nude mice. This was evident from inhibition of estrogen-induced breast tumor formation in the xenograft model by both overexpression of catalase as well as by co-treatment with Ebselen. To understand how 4-OH-E2 induces this malignant phenotype through ROS, we investigated the effects of 4-OH-E2 on redox-sensitive signal transduction pathways. During the malignant transformation process we observed that 4-OH-E2 treatment increased AKT phosphorylation through PI3K activation. The PI3K-mediated phosphorylation of AKT in 4-OH-E2-treated cells was inhibited by ROS modifiers as well as by silencing of AKT expression. RNA interference of AKT markedly inhibited 4-OH-E2-induced in vitro tumor formation. The expression of cell cycle genes, cdc2, PRC1 and PCNA and one of transcription factors that control the expression of these genes - nuclear respiratory factor-1 (NRF-1) was significantly up-regulated during the 4-OH-E2-mediated malignant transformation process. The increased expression of these genes was inhibited by ROS modifiers as well as by silencing of AKT expression. These results indicate that 4-OH-E2-induced cell transformation may be mediated, in part, through redox-sensitive AKT signal transduction pathways by up-regulating the expression of cell cycle genes cdc2, PRC1 and PCNA, and the transcription factor - NRF-1. In summary, our study has demonstrated that: (i) 4-OH-E2 is one of the main estrogen metabolites that induce mammary tumorigenesis and (ii) ROS-mediated signaling leading to the activation of PI3K/AKT pathway plays an important role in the generation of 4-OH-E2-induced malignant phenotype of breast epithelial cells. In conclusion, ROS are important signaling molecules in the development of estrogen-induced malignant breast lesions