Lightweight Self-Compacting Concrete Incorporating Industrial Rejects and Mineral Admixtures: Strength and Durability Assessment

By the recent global research developments, a lot of natural and artificial materials that are normally discarded and landfilled, are continually investiga     

Carbothermal Synthesis of Nanocrystalline Aluminum Nitride Powders

A new precursor technique for the carbothermal synthesis of nanocrystalline AlN powder has been developed. A precursor that contains an intimate mixture of nanocrystalline Al₂O₃ and carbon has been synthesized by using a chemical pyrophoric reaction. The formation of AlN starts at 1473 K, and complete conversion has been observed at temperatures >1673 K. The synthesized AlN particles are nanocrystalline (<100 nm) in size.     

The suppression of eicosanoid synthesis by peritoneal macrophages is influenced by the ratio of dietary docosahexaenoic acid to linoleic acid

The efficacy of docosahexaenoic acid (DHA) in suppressing eicosanoic synthesis by peritoneal macrophagesin vivo was influenced by the relative amount of dietary DHA when linoleic acid (LA) was held constant. Increasing DHA from 0 to 37% of the fatty acids in diets containing 10 weight % fat (of which LA was 40%) caused an eleven-fold increase in the DHA content of macrophages. Limited retroconversion of DHA to eicosapentaenoic acid was observed. Macrophages in animals consuming DHA synthesized significantly lower amounts of leukotriene E₄, prostaglandin E₂ and 6-keto prostaglandin F_1α in vivo upon stimulation with zymosan. The maximum inhibition of eicosanoid synthesis was observed when the dietary DHA/LA ratio was 0.16 and no further inhibition occurred when the ratio was increased up to 0.81.     

A Rectangular SRR Switched Slotted Microstrip Patch for Frequency Diversity Application

Planar antenna with a specific resonant mode is essential to meet the diversity demand for wireless communication. This paper presents modeling and experimental validation of a microstrip antenna design in which multiple resonant frequencies are excited based on different negative permeability response of the rectangular split ring resonator (SRR). The antenna geometry consists of a slotted patch with split ring resonator loaded between its two arms. The patch was fabricated on FR-substrate of relative permittivity ε_r?=?4.4, and has a size of 30.5 mm?×?34 mm. In the antenna desing, PIN diodes connect the outer ring and inner ring resonator of the SRR to the adjacent arms of the patch. Under various bias conditions, quad-band resonance was observed at 2.07 GHz, 2.11 GHz, 2.31 GHz, and 2.46 GHz. The measured S₁₁ results are found comparable to the simulated data, and demonstrate proper functioning of the proposed antenna with stable gain and radiation patterns.     

Rats fed blended oils containing coconut oil with groundnut oil or olive oil showed an enhanced activity of hepatic antioxidant enzymes and a reduction in LDL oxidation

The effects of feeding Wistar rats with blended and interesterified oils of coconut (CO):groundnut (GNO) or CO:olive (OLO) on liver antioxidant enzyme activities and susceptibility of LDL to oxidation were studied. The hepatic lipid peroxidation (LPO) levels in the rats fed CO:GNO blend and interesterified oils were increased by 31% and 21%, when compared to the rats given CO. The superoxide dismutase activity was increased by 31% and 28%, and catalase (CAT) activity was increased by 37% and 39%, respectively, in rats given blends and interesterified oils of CO:GNO, as compared to those given CO. The activities of glutathione peroxidase (GPx) were increased by 17% and 20% in rats given CO:GNO blend and interesterified oils. Glutathione transferase (GST) level was also found to be increased by 26% and 31% after feeding blended and interesterified oils of CO:GNO, compared to those given CO. The LDL oxidation, which was elevated by feeding GNO, was found to be reduced by 10% and 14%, respectively, in the groups fed blended and interesterified oils of CO:GNO. Similarly, CO:OLO blended oils enhanced SOD, CAT, GPx and GST activities by 34%, 43%, 27% and 23%, respectively, compared to the rats given CO-containing diets. The corresponding increases in theses antioxidant enzyme activities when CO:OLO interesterified oils were fed to rats were 38%, 50%, 28% and 26%, respectively, when compared to rats given CO-containing diets. There was a significant reduction in hepatic LPO as well as oxidation of LDL, when blended and interesterified oils of CO:OLO were fed to rats. The results demonstrated that blended and interesterified oils of CO with GNO or OLO enhance hepatic antioxidant enzymes, decreased lipid peroxidation in liver and reduced the susceptibility of LDL to oxidation.     

Effect of Heating Rates on the Synthesis of Al2O3–SiC Composites by the Self-Propagating High-Temperature Synthesis (SHS) Technique

Various aspects of in situ formation of Al₂O₃–SiC composites by the self-propagating high-temperature synthesis (SHS) technique have been investigated using thermal analyses (TG/DTA) of a powder mixture (4Al, 3SiO₂, 3C) and pellets in an argon atmosphere at different heating rates. Both the reaction initiation and peak temperatures are found to increase with the heating rates. At lower heating rates, the powder samples do not reveal any exothermic peak possibly because of poor reactivity and sluggish exothermic reaction. The appearance of exothermic peaks in the DTA plots after melting of aluminum indicates reduction of silica by liquid aluminum. Conversion of aluminum is found to decrease marginally with an increase in heating rates. The apparent activation energy of the process compares well with the interdiffusion activation energy of silicon and oxygen, indicating that oxygen diffusion in Si formed at the reaction front may be the rate-controlling factor for this SHS process. From SEM studies it appears that the formation of SiC whiskers is through liquid-phase mass transfer.     

High-capacity hydrogen storage in lithium and sodium amidoboranes

The safe and efficient storage of hydrogen is widely recognized as one of the key technological challenges in the transition towards a hydrogen-based energy economy. Whereas hydrogen for transportation applications is currently stored using cryogenics or high pressure, there is substantial research and development activity in the use of novel condensed-phase hydride materials. However, the multiple-target criteria accepted as necessary for the successful implementation of such stores have not yet been met by any single material. Ammonia borane, NH3BH3, is one of a number of condensed-phase compounds that have received significant attention because of its reported release of approximately 12 wt% hydrogen at moderate temperatures (approximately 150 degrees C). However, the hydrogen purity suffers from the release of trace quantities of borazine. Here, we report that the related alkali-metal amidoboranes, LiNH2BH3 and NaNH2BH3, release approximately 10.9 wt% and approximately 7.5 wt% hydrogen, respectively, at significantly lower temperatures (approximately 90 degrees C) with no borazine emission. The low-temperature release of a large amount of hydrogen is significant and provides the potential to fulfil many of the principal criteria required for an on-board hydrogen store.