132 research outputs found

    Plant Regeneration And Biochemical Changes in Rice (Oryza Sativa L.) Under NaCl Stress

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    This project was designed to examme the effects of NaCI on growth and regeneration of callus and cell suspension cultures of the five rice cultivars namely, Puteh Perak, Mahsuri, Basmati-370, Nona Bokra and Khari Gunja. In addition, changes of nitrogen assimilating enzymes, phosphatase and some dehydrogenase of Kreb's Cycle in cell suspension cultures of Basmati-370 and Puteh Perak were also investigated. The callus cultures were induced from embryo section of seeds of rice using MS solid media containing 10 µM 2,4-D and 2 µM kinetin. Cell suspension cultures were initiated in liquid media from the induced embryogenic callus of rice using salts of the B5 media containing 10 µM 2,4-D. The five rice cultivars tested had high rates of callus induction (80-88%). In the one step NaCI treatment, the growth of control callus and cell suspension cultures of the five rice cultivars decreased and significant morphological changes were observed. At 180 mM NaCI treatment , the reduction in callus growth was 29, 36, 42, 32 and 42% while at 70 mM NaCl, reduction in the growth of cell suspension culture was 38, 53, 58, 41 and 55% in Puteh Perak, Mahsuri, Basmati-370, Nona Bokra and Khari Gunj a, respectively compared to the control culture without NaCI (100%). The callus growth was completely retarded at 540 mM NaCI treatment while in cell suspension it was at 210 mM NaCl. The multiple step NaCl-treated callus and cell suspension cultures of the five rice cultivars produced higher growth (% dry weight) in the presence of NaCI compared to the control cultures. The callus and cell suspension of the five rice cultivars on high NaCl containing media reached a maximum growth at range of 10-1 3th passages and 6-9th passages, respectively while the control cultures proliferated at constant rate. The multiple step NaCl-treated cell suspension of Basmati:J70 showed stability to NaCI treatment compared to the control. MS solid regeneration media containing 3 /-lM lAA and 40 /-lM kinetin was most suitable for plant regeneration of callus and cell suspension of five rice cultivars. The plant regeneration capacity of one step NaCl-treated callus and cell suspension cultures of the five rice cultivars decreased with the increased concentrations of NaCI in the treatment media. Higher regeneration frequencies were observed from multiple step NaCl-treated callus of Puteh Perak, Mahsuri and Nona Bokra and cell suspension cultures of Puteh Perak and Nona Bokra compared to the control while lower regeneration than the control was obtained in other cultivars. The plant regeneration capacity of multiple step NaCl-treated and control cultures decreased with the increase in culture age. However, NaCl-treated cultures maintained higher regeneration capacity for up to 48 weeks of culture compared to the control. The growth rate of cell suspension of Basmati-370 increased from day 4 up to day 1 0 and the activities of ACP, ALP, GS, MDH, NADP-ICDH and SDH were highest on day 10 while GDH and GOGAT on day 8 and NR on day 6 during the 14 days of culture period. The activities of GDH, GOGAT, NR, ACP, ALP, MDH and NADP-ICDH extracted from NaCI-treated cell suspension of Basmati-3 70 increased while GS and SDH activities decreased. The activities of GDH, NR, ALP and MDH decreased in cell suspension of Puteh Perak but increased in Basmati-370 under increasing NaCI treatments. The GS and SDH activities increased in the presence of NaCI of Puteh Perak but decreased in Basmati-370 and the GOGAT, ACP and NADPICDH increased by NaCI in both cultivars tested. The addition of NaCI (0-200/-lM) to the assay mixture resulted in increased specific activities of GDH, NR, GOGAT, ACP, MDH and NADP-ICDH at low concentration but decreased the activities at high concentrations while the specific activities of GS, ALP and SDH continously decreased. Changes in selected enzyme activities of cell suspension of rice due to NaCI indicates that NaCl interferes with nitrogen and phosphorus metabolism

    Reflective Crack Mitigation Using AST Interlayer over Soil-Cement Base for Flexible Pavements

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    Flexible pavement over soil-cement base deteriorates over time due to reflective cracking caused by the shrinkage of such base. The propagation of the reflective cracks in overlaying hot mix asphalt (HMA) could be mitigated by installing interlayer system. State of Louisiana, USA has been utilizing Asphaltic Surface Treatment (AST) as an interlayer between the soil-cement base and HMA to mitigate reflective cracking. To evaluate the field performance of AST interlayer, flexible pavement projects with and without AST interlayer over soil-cement bases were compared in this study. From the Pavement Management System (PMS) database of Louisiana, 27 AST interlayer projects (70 miles) and 46 No AST interlayer projects (175 miles) were selected for comparison. The service lives of these projects were assessed using the time series cracking, rutting, and international roughness index (IRI) data. It was found that the projects with AST interlayer produced on average 14.3 and 14.7 years of service lives for transverse and alligator cracking, respectively. On the other hand, the average service lives of No AST interlayer projects were 11.6 and 12.5 years for such cracks, respectively. Hence, the AST interlayer projects gained 2.7 and 2.2 years of service life for transverse and alligator cracking, respectively. However, the service life based on rut data showed a loss of 3.2 years for AST interlayer projects (16.2 years). Furthermore, the longitudinal cracking and IRI exhibited no improvements. In summary, AST interlayer can mitigate transverse and alligator cracking but slightly increase the rutting potential of the pavement

    Mitigating Reflective Cracking Through the Use of a Ductile Concrete Interlayer

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    Reflective cracking is considered one of the most important issues that causes premature deterioration of composite pavements. Many types of mitigation methods have been studied in the past. However, they are either not effective in delaying the reflective cracking, or they only extend the service life by a few years. To address this critical issue and significantly extend the service life of the composite pavement, in this research, a ductile interlayer made of engineered cementitious composites (ECC) was proposed. It was hypothesized that by adding a thin layer of highly ductile ECC material between the existing pavement and overlay, reflective cracking could be arrested by the ductile interlayer. This study experimentally evaluated the effectiveness of ECC as an interlayer system. A laboratory test protocol was designed to simulate repeated traffic loads to measure the fatigue performance of ECC interlayer system. The strain field and reflective cracking were monitored using digital image correlation (DIC) technique. It was found that the composite pavement specimens with ECC interlayer provided significantly higher fatigue life as compared to the control specimens without an interlayer. The failure mode also changed from single reflective crack to multiple cracks in overlaid HMA mixtures. The results indicated that ECC could be used as a potential effective interlayer system to retard or mitigate reflective cracking

    Mechanical and Durability Characteristics of Roller Compacted Geopolymer Concrete Using Reclaimed Asphalt Pavement

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    Every year a large quantity of reclaimed asphalt pavement (RAP) is generated in the USA. Utilization of RAP can solve the storage problem, prevent environmental pollution and reduce construction costs. This study focuses on the strength and durability characteristics of RAP mixtures by introducing the concept of roller-compacted fly ash-based geopolymer concrete (RCGPC). Several selected RCGPC mixtures were investigated to evaluate the effect of mixture variables, including sodium hydroxide (NaOH) molarity, sodium silicate (Na2SiO3) to sodium hydroxide (NaOH) ratio on the strength, modulus and durability characteristics of the mixtures. The effects of different curing temperature and curing duration on compressive strength were also studied. It was found that the mixtures with Na2SiO3/NaOH ratio of 1 yielded about 12 % higher compressive strength than the ratio of 0. Further, the mixtures using 10M NaOH and alkali ratio of 1 produced about 25% higher compressive strength than 8M NaOH which produced about 17 MPa. Similar results were obtained for elastic modulus and split tensile strength of the mixtures. Freeze-thaw durability tests also revealed acceptable results for the RCGPC mixtures. Formation of new geopolymeric compounds and chemical bonds in the newly formed novel RCGPC mixtures were also discovered using XRD analysis. The comparison of mechanical and durability testing further showed that RCGPC performed better than the roller-compacted cement concrete (RCC) using RAP. Based on the results and analysis the developed RCGPC using RAP could be used as a cost-effective solution for the construction of pavement structures

    Modeling Probability of Path Loss for DSDV, OLSR and DYMO above 802.11 and 802.11p

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    This paper presents path loss model along with framework for probability distribution function for VANETs. Furthermore, we simulate three routing protocols Destination Sequenced Distance Vector (DSDV), Optimized Link State Routing (OLSR) and Dynamic MANET On-demand (DYMO) in NS-2 to evaluate and compare their performance using two Mac-layer Protocols 802.11 and 802.11p. A novel approach of this work is modifications in existing parameters to achieve high efficiency. After extensive simulations, we observe that DSDV out performs with 802.11p while DYMO gives best performance with 802.11.Comment: IEEE 8th International Conference on Broadband and Wireless Computing, Communication and Applications (BWCCA'13), Compiegne, Franc

    Autoclaved tumor bone for reconstruction: An alternative in developing countries

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    The options for reconstruction after excision of skeletal tumors include reimplanting the autoclaved tumor-bearing bone. We asked whether such bone will survive and unite with normal bone and whether the local tumor recurrence rate increases after its use. We ascertained the functional outcome (Musculoskeletal Tumor Society score) and complications in 19 patients. After wide excision, the bony segment was autoclaved at 120 degrees for 10 minutes and reimplanted at the original defect with intramedullary nails and compression plates. Twelve of our 19 patients were available for followup. The autoclaved segment united with the normal bone in 11 of the 12 patients. No patients had fracture or resorption of the autoclaved segment. Two patients had local tumor recurrence in nearby soft tissues, apparently unrelated to the autoclaved bone. The mean functional score was 70%. Complications included fatigue failure of the nail in one patient, superficial infection in three patients, and deep infection in two patients. Reconstruction with autoclaved tumor-bearing bone is a simple and effective tool in limb salvage. This technique is a cost-effective alternative for developing countries circumventing complications of prosthetic and allograft reconstruction

    Experimental Evaluation of Engineered Cementitious Composites as Reflective Crack Control Interlayer for Composite Pavements

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    Reflective cracking at transverse joints is considered as a predominant distress in composite pavements. Various interlayers have been used previously to prevent or retard reflective cracking. Engineered cementitious composite (ECC) is a special type of high-performance fiber-reinforced cementitious material that is expected to perform better as an interlayer due to its higher tensile strength and ductility. This study aims to evaluate the effectiveness of ECC as an interlayer system experimentally. A laboratory test protocol was designed to simulate repeated traffic loads to measure the fatigue performance of ECC interlayer system using digital image correlation (DIC) technique. It was found that the composite pavement specimens with ECC interlayer provided significantly higher fatigue life as compared to the control specimens without interlayer. This result indicates that ECC could be used as a potential effective interlayer system to retard or mitigate reflective cracking
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