Quantitative Modeling of Polymer Scratch Behavior

Scratch-induced surface deformation is a complex mechanical process due to high strain rate large-scale deformation, non-linear material response, heat dissipation and complex stress field evolved during the process. The rate, time, temperature and pressure dependent behavior of polymers, and the surface condition of the interacting surfaces also add to the complexity. In order to gain in-depth understanding of polymer scratch behavior; this dissertation focuses on numerical analysis and experimental study of scratch-induced deformation in polymers, leading to quantitative prediction of scratch behavior of model amorphous polymers. A comprehensive three-dimensional finite element method (FEM) parametric study has been performed by incorporating key characteristics of polymer constitutive behavior to investigate the effect of material parameters and surface properties on the evolution of scratch-induced deformation in polymers, along with relevant experimentation. The qualitative analyses using FEM simulation and experimental work suggest that indeed correlation between material and surface properties, and scratch-induced damage mechanisms can be established. To quantitatively predict the scratch behavior of polymers via FEM, PC and SAN model systems are chosen. A modification of Ree-Eyring theory is used to assess the rate dependent behavior of model polymers at high strain rates based on the experimental data obtained at low strain rates. By including the rate and pressure dependent mechanical behavior and pressure dependent frictional behavior in the FEM model, good agreement has been found between FEM simulation and experimental observations. The results suggest that, by including proper constitutive relationship and friction model in the numerical analysis, the scratch behavior of polymers can be quantitatively predicted with reasonable success

Effects of aflatoxin contaminated feed on the fingerlings of tilapia (Oreochromis niloticus Linnaeus, 1758)

Aflatoxin contamination, particularly common in cultured fishes in Asian countries, are considered unsafe both for fish and human health. However, the presence of aflatoxin in cultured fish feed and their effect are still under estimated in Bangladesh. The present study aimed to assess the effects of aflatoxin on growth performance and residues in tilapia (Oreochromis niloticus) fingerlings. Fish feed were treated with several concentration of aflatoxin as 0 ppb (T0, control), 25 ppb (T1), 50 ppb (T2) and 100 ppb (T3) and fed the tilapia fingerlings (n=10) in individual glass aquaria (24×12×12 inch, 105-litre capacity) conditions for 12 weeks. Comparatively higher body length (cm) and weight gain (g) were observed in treatment T0 (1.68 and 4.98) and T1 (1.60 and 5.48) than those of treatment T2 (1.31 and 4.06) and T3 (1.20 and 3.10), respectively. The specific growth rate (SGR) were almost similar in treatment T0 (52%), T1 (51%) and T2 (52%) whereas declined significantly (p<0.05) in T3 (39%). Higher survival rate was also demonstrated in treatment T0 (90%) and T1 (90%) whereas significantly decreased in treatment T2 (60%) and T3 (40%). The residue of aflatoxin was not detected in T0 and T1. On the contrary, the residual effect in tilapia fingerling was evident in T2 and T3 treatment. The findings of the present study revealed that aflatoxin contaminated feed is harmful for the growth performance and survival of O. niloticus fingerlings. Further study is necessary to safeguard the aquaculture production as well as to produce healthy food for human consumption

Assessment of heavy metals concentration in water and Tengra fish (Mystus vittatus) of Surma River in Sylhet region of Bangladesh

The study was carried out to assess the concentration of heavy metals in water and Tengra fish (Mystus vittatus) of the Surma River, the largest water basin ecosystem covering the north-eastern parts of Bangladesh. Water and Tengra fish (M. vittatus) samples were collected from a total of six sampling stations in which three sampling stations were in Sylhet district and the rest three were in Sunamganj district. Samples were collected from February 2017 to June 2017 on a monthly basis. Water and Tengra fish (M. vittatus) samples were analyzed for the detection of heavy metals viz., lead (Pb), chromium (Cr) and cadmium (Cd) concentrations. Atomic absorption spectrophotometry was used for the detection of heavy metals after digestion of the samples. Pb and Cr were detected from both water and Tengra fish (M. vittatus) samples collected from all the six sampling stations of Sylhet and Sunamganj district. But, Cd was not found both in water and Tengra fish (M. vittatus) during the study period. This study concluded that the detected concentrations of metals (Pb and Cr) in the studied Tengra fish (M. vittatus) muscles were accepted by the international legislation limits and are safe for human consumption. But in water, Pb is the only metal that potentially poses the ecological risk to the water body as it exceeds the acceptance level recommended by World Health Organization (WHO). Consequently, close monitoring of metals pollution of the Surma River is recommended with a view to minimizing the health risk of the population that depend on the river for their water and fish supply

Integrated management of Fusarium wilt of chickpea (Cicer arietinum L.) caused by Fusarium oxysporum f. sp. ciceris with microbial antagonist, botanical extract sp. ciceris with microbial antagonist, botanical extract

The present study was carried out to assess the efficacy of an integrated management strategy for Fusarium wilt of chickpea that combined the use of microbial antagonist, botanical extract and fungicide. Before setting the experiment in field micro plots, a series of in vitro and in vivo experiments were conducted to select a virulent isolate of F. oxysporum f. sp. ciceris, an effective antagonistic isolate of Trichoderma harzianum, a fungitoxic botanical extract and an appropriate fungicide. The isolate FS1 of F. oxysporum f. sp. ciceris appeared to be most virulent to chickpea cultivar BU-Chola-1 and selected as test pathogen. Among the 20 isolates screened, T. harzianum isolate T-75 showed the highest (75.89%) inhibition of the radial growth of F. oxysporum f. sp. ciceris in dual culture assay on PDA. Absolute inhibition (100.00%) of colony growth of F. oxysporum f. sp. ciceris was observed where fungicide Provax-200 at 100 ppm was used. Azadirachta indica leaf extract gave maximum inhibition (55.19%) of radial growth of F. oxysporum f. sp. ciceris at all concentrations. The integration of soil treatment with T. harzianum isolate T-75 and Az. indica leaf extract and seed treatment with Provax-200 appeared to be significantly superior in reducing Fusarium wilt and in improving seed yield of chickpea compared to any single or dual application of them in the field. The results of this study exhibit the importance of integrating selective microbial antagonist, botanical extract and fungicide to achieve appropriate management of Fusarium wilt and increase of seed yield in chickpea in Bangladesh.Keywords: Integrated management, Fusarium wilt, Fusarium oxysporum f. sp. ciceris, chickpea (Cicer arietinum L.), antagonists, botanicals, fungicides.African Journal of Biotechnology Vol. 12(29), pp. 4699-470

<i>Sclerotinia sclerotiorum</i> (Lib.) de Bary: Insights into the Pathogenomic Features of a Global Pathogen

Sclerotinia sclerotiorum (Lib.) de Bary is a broad host-range fungus that infects an inclusive array of plant species and afflicts significant yield losses globally. Despite being a notorious pathogen, it has an uncomplicated life cycle consisting of either basal infection from myceliogenically germinated sclerotia or aerial infection from ascospores of carpogenically germinated sclerotia. This fungus is unique among necrotrophic pathogens in that it inevitably colonizes aging tissues to initiate an infection, where a saprophytic stage follows the pathogenic phase. The release of cell wall-degrading enzymes, oxalic acid, and effector proteins are considered critical virulence factors necessary for the effective pathogenesis of S. sclerotiorum. Nevertheless, the molecular basis of S. sclerotiorum pathogenesis is still imprecise and remains a topic of continuing research. Previous comprehensive sequencing of the S. sclerotiorum genome has revealed new insights into its genome organization and provided a deeper comprehension of the sophisticated processes involved in its growth, development, and virulence. This review focuses on the genetic and genomic aspects of fungal biology and molecular pathogenicity to summarize current knowledge of the processes utilized by S. sclerotiorum to parasitize its hosts. Understanding the molecular mechanisms regulating the infection process of S. sclerotiorum will contribute to devising strategies for preventing infections caused by this destructive pathogen

Seasonal Dynamics of Heavy Metal Concentrations in Water and Fish from Hakaluki <i>Haor</i> of Bangladesh

Food safety is currently a serious concern due to the health risks associated with food intake, particularly due to heavy metal contamination. Therefore, the present study was conducted to investigate the heavy metals concentration in water and fishes collected from Hakaluki haor, Bangladesh. Three important fish species, Labeo rohita, Cirrhinus cirrhosis, and Labeo calbasu, together with water samples, were analyzed for heavy metals (Pb, Cr, and Cd), respectively. Considering four seasons, namely the monsoon, post-monsoon, winter, and pre-monsoon, a total of 72 fish samples were collected from three fishing stations from June 2017 to May 2018. The results showed that the total mean concentration of metals in water (mg L−1) was found to be in the order of Pb (0.125 ± 0.058) > Cr (0.026 ± 0.012) > Cd (0.001 ± 0.0002) within the maximum permissible limits set by the EU and WHO, except for Pb concentrations. Similarly, the total mean concentrations of Pb in fish (µg g−1) were found in order of L. rohita (0.388 ± 0.291) > Cirrhinus cirrhosus (0.334 ± 0.236) > L. calbasu (0.251 ± 0.117) greater than the maximum permissible limits (0.3 µg g−1) set by FIQC, except for L. calbasu. However, the mean concentrations of Cr and Cd in fish were found to be below the maximum permissible limits of FAO and FIQC, respectively. The quantity of heavy metal contamination in this haor indicates that the situation is worrying for the region’s biota and residents. However, to protect public health and reduce environmental risk, the appropriate authorities should oversee and monitor it with strong hands

Evaluation of bioactivities of methanol and petroleum ether extracts of Cassia renigera seed

Abstract Background To investigate in vitro antioxidant, brine shrimp lethality bioassay, antimicrobial, anthelmintic activities and in vivo peripheral analgesic activity of methanol and petroleum ether extracts of Cassia renigera seed. Methods Phytochemical screening of the crude extracts was carried out. Antioxidant activity was determined using seven different methods. Brine shrimp lethality bioassay and anthelmintic activities were done using nauplii of Artemia salina and adult earthworm (Pheretima posthuma), respectively. The antimicrobial potential was investigated against three Gram-positive and three Gram-negative bacteria. Acetic acid induced writhing test was performed to evaluate peripheral analgesic activity. Results Both methanol and petroleum ether extracts showed the presence of flavonoids, saponins, and tannins. While alkaloids, glycosides, and steroids were only found in the methanolic extract. Methanolic extract showed more potent 1,1- diphenyl-2-picrylhydrazyl (DPPH), nitric oxide scavenging capacity, cupric reducing and reducing power capacity than petroleum ether extract. While petroleum ether extract showed better results in total phenol and total antioxidant activities. In brine shrimp lethality bioassay methanolic and petroleum ether extracts showed the LC50 value of 74.44 and 121.49 μg/mL, respectively. In overall antimicrobial study methanolic extract showed better activity than petroleum ether extract. Methanolic extract of 50 mg/mL showed maximum anthelmintic activity comparable to the standard (Piperazine Citrate, 10 mg/mL). Both 500 mg/kg and 1000 mg/kg body weight dose of the methanolic extract exhibited significant 39.64% and 58.73% writhing inhibition (푃< 0.05) in test animals, consecutively. Conclusions In a nutshell, the results suggested that the seed can be used as a potential source for the aforesaid bioactivities

Seasonal Dynamics of Heavy Metal Concentrations in Water and Fish from Hakaluki Haor of Bangladesh

Food safety is currently a serious concern due to the health risks associated with food intake, particularly due to heavy metal contamination. Therefore, the present study was conducted to investigate the heavy metals concentration in water and fishes collected from Hakaluki haor, Bangladesh. Three important fish species, Labeo rohita, Cirrhinus cirrhosis, and Labeo calbasu, together with water samples, were analyzed for heavy metals (Pb, Cr, and Cd), respectively. Considering four seasons, namely the monsoon, post-monsoon, winter, and pre-monsoon, a total of 72 fish samples were collected from three fishing stations from June 2017 to May 2018. The results showed that the total mean concentration of metals in water (mg L&minus;1) was found to be in the order of Pb (0.125 &plusmn; 0.058) &gt; Cr (0.026 &plusmn; 0.012) &gt; Cd (0.001 &plusmn; 0.0002) within the maximum permissible limits set by the EU and WHO, except for Pb concentrations. Similarly, the total mean concentrations of Pb in fish (&micro;g g&minus;1) were found in order of L. rohita (0.388 &plusmn; 0.291) &gt; Cirrhinus cirrhosus (0.334 &plusmn; 0.236) &gt; L. calbasu (0.251 &plusmn; 0.117) greater than the maximum permissible limits (0.3 &micro;g g&minus;1) set by FIQC, except for L. calbasu. However, the mean concentrations of Cr and Cd in fish were found to be below the maximum permissible limits of FAO and FIQC, respectively. The quantity of heavy metal contamination in this haor indicates that the situation is worrying for the region&rsquo;s biota and residents. However, to protect public health and reduce environmental risk, the appropriate authorities should oversee and monitor it with strong hands