Nitrogen utilization by lowland rice as affected by fertilization with urea and green manure

Field studies were conducted during two consecutive wet seasons in flooded rice (Oryza sativa L.) to determine the effect of green manure on urea utilization in a rice-fallow-rice cropping sequence. Replicated plots were fertilized with 60 to 120 kg of urea N ha^–1 in three split applications (50, 25 and 25%) with or without incorporation of dhaincha (Sesbania aculeata L.) (100 kg N ha^–1). During the first crop only 31 to 44% of the urea added was used by the rice. Incorporatingin situ grown dhaincha (GM) into the soil at transplanting had little effect on urea utilization. Forty-four to 54% of the N added was not recovered in the soil, rice crop, or as nitrate leachate during the first cropping season. Incorporation of GM had no effect on fertilizer N recovery. Only about 2% of the urea N added to the first rice crop was taken up by the second rice crop and, as in the first crop, the GM had little effect on residual N, either in amount or utilization.     

Stepwise transplantation of an active site loop between heat-labile enterotoxins LT-II and LT-I and characterization of the obtained hybrid toxins

Members of the cholera toxin family, including Escherichia coli heat-labile enterotoxins LT-I and LT-II, catalyze the covalent modification ofintracellular proteins by transfer of ADP-ribose from NAD to a specificarginine of the target protein. The ADP-ribosylating activity of thesetoxins is located in the A-subunit, for which LT-I and LT-II share a 63%sequence identity. The flexible loop in LT-I, ranging from residue 47 to56, closes over the active site cleft. Previous studies have shown thatpoint mutations in this loop have dramatic effects on the activity of LT-I.Yet, in LT-II the sequence of the equivalent loop differs at four positionsfrom LT-I. Therefore five mutants of the active site loop were created by astepwise replacement of the loop sequence in LT-I with virtually all thecorresponding residues in LT- II. Since we discovered that LT-II had noactivity versus the artificial substratediethylamino-benzylidine-aminoguanidine (DEABAG) while LT-I does, ouractive site mutants most likely probe the NAD binding, not the argininebinding region of the active site. The five hybrid toxins obtained (Q49A,F52N, V53T, Q49V/F52N and Q49V/F52N/V53T) show (i) great differences inholotoxin assembly efficiency; (ii) decreased cytotoxicity in Chinesehamster ovary cells; and (iii) increased in vitro enzymatic activitycompared with wild type LT-I. Specifically, the three mutants containingthe F52N substitution display a greater Vmax for NAD than wild type LT-I.The enzymatic activity of the V53T mutant is significantly higher than thatof wild type LT-I. Apparently this subtle variation at position 53 isbeneficial, in contrast to several other substitutions at position 53 whichpreviously had been shown to be deleterious for activity. The most strikingresult of this study is that the active site loop of LT- I, despite greatsensitivity for point mutations, can essentially be replaced by the activesite loop of LT-II, yielding an active 'hybrid enzyme' as well as 'hybridtoxin'.     

An experimental investigation of subsurface ground temperature in Texas: a complete study

This paper describes the results of experimental studies conducted in Houston, Texas from June 1997 to May 1998 to determine seasonal variations of subsurface ground temperature. The results indicate that the average ambient temperature is 89.31°F (31.84°C) in summer (June–October), and 63.93°F (17.74°C) in winter (November–February). The ground temperature at depths greater than 10 feet remains relatively constant through the year. At a depth of 10 feet (3.04 m), the average ground temperature is 75.12°F (23.96°C) in summer and 75.87°F (24.37°C) in winter. The observed temperature differential between the ambient and the ground temperature at 10 feet is 8–17°F (4.4–9.4°C). The temperature differential suggests that there is potential for pre-heating and pre-cooling the ambient air used in conditioning commercial and institutional buildings. The least square fit equations to project average monthly subsurface ground temperatures are presented.     

Effect of exhaust gas recirculation on a nanoparticle-doped biodiesel- and diesel-blends-fuelled diesel engine

ABSTRACT

This work investigates the effect of adding Cerium oxide nanoparticles at different proportions (30, 60 and 90?ppm) to Calophyllum inophyllum methyl ester and diesel blends (20% CI methyl ester and 80% diesel) in a four-stroke single-cylinder diesel engine. Addition of nanoparticles is a strategy to reduce emission and to improve the performance of the biodiesel. Modified fuels are introduced into the engine by admitting exhaust gas recirculation (EGR) at a rate of 10% and 20% so as to reduce nitrogen oxide (NO_X) emissions from biodiesel and diesel blends. Results revealed a significant reduction in emissions (CO, NO_X, HC and Smoke) at a 10% EGR rate. However, brake thermal efficiency is reduced with an increase in brake-specific fuel consumption at higher EGR rates. Hence, it is observed that 10% EGR rate is an effective method to control the emission of biodiesel and diesel blends without compromising much on engine efficiency.     

Influence of injection timing on cerium oxide nanoparticle doped in waste cooking palm oil bio-diesel and diesel blends fuelled in diesel engine

ABSTRACT

Injection timing (IT) is a vital factor among different injection parameters which governs the emissions and performance factors of the engine. This work portrays the effect of IT on cerium oxide nanoparticle doped Waste Cooking Palm Oil biodiesel and diesel blends. The doping is made at 30, 60 and 90?ppm. The modified fuels are introduced in reducing IT of 19°, 21° and 23°bTDC. 1500?rpm engine is made use in this study. Results revealed a significant reduction in emissions (CO, NO_X, HC and Smoke) at IT?=?23°bTDC. Furthermore, performance (BSFC, BTE) is improved for fuel blends at IT?=?23°bTDC.     

Diurnal and seasonal variabilities in surface ozone and its precursor gases at a semi‐arid site Anantapur (14.62°N, 77.65°E, 331 m asl) in India

Measurements of surface ozone and its precursor gases (NO_x and CO) have been made at a semi‐arid site Anantapur (14.62°N, 77.65°E, 331 m asl) in tropical Indian region for the period, 2001–2003. NO_x and CO levels were the highest during morning and late night hours at this site. Diurnal variations of ozone concentrations varied from 25 ppbv to 50 ppbv and were observed to increase gradually after sunrise, attaining a maximum value by the evening and decreasing gradually thereafter. During monsoon months, the diurnal amplitude of ozone was found to be small (20–25 ppbv). Seasonal variation in ozone showed a pronounced maximum (40–50 ppbv) in the winter and summer. Local pollutants were major contributors to the ozone levels during this period. Ozone shows a yearly mean mixing ratio of about 35.9 ± 8.8 ppbv. The daytime concentration of CO and NO_x varied between 200 to 1200 ppbv and 3 to 20 ppbv respectively for the period studied. Annual average mixing ratios of oxides of nitrogen (NO_x) and CO were observed to be 3.9±0.6 ppbv and 436±64 ppbv, respectively.     

Effect of CNG flow rate on the performance and emissions of a Mullite-coated diesel engine under dual-fuel mode

On the diesel engines that are used to generate power in transportation and industries, many researchers have to deal with major problems of smoke emissions while extracting higher efficiency. There are many studies which reported the exhaust emission reduction strategies from diesel engines by applying new combustion methods that are capable of mitigating the formation of harmful emissions. One of the methods to reduce the exhaust emissions in diesel engines is to use the dual-fuel combustion mode. In this study, an attempt has been made to evaluate the effect of thermal barrier coating (TBC) on the dual-fuel engine and for this, experiments are carried out on a single-cylinder direct-injection diesel engine under dual-fuel and low heat rejection mode with compressed natural gas (CNG) as gaseous fuel. Engine components that are exposed to the combustion are coated with Mullite (3Al₂O₃-2SiO₂) TBC. Diesel at 200 bar injector opening pressure was used as pilot fuel and CNG at different flow rates (5, 10 and 15 litres per minute) was inducted into the combustion chamber through inlet manifold as main fuel. Experimental results show that the coating of TBC on the engine components has a positive effect on the performance emissions of the dual-fuel test engine. Brake specific fuel consumption (BSFC) was found improved significantly at all flow rates of CNG with coated engine. Emissions on the other hand were also noticed to be on the lower side with the coated engine except NO_x. Smoke emissions were significantly reduced with coated CNG operation of the test engine at all flow rates.     

Effects of porous carbon on sintered Al-Si-Mg matrix composites

The influence of microporous particulate carbon char on the mechanical, thermal, and tribological properties of wear-resistant Al-13.5Si-2.5Mg alloy composites was studied. Large increases in surface area due to the formation of micropores in coconut shell chars were achieved by high-temperature activation under CO₂ gas flow. Activated char particles at 0.02 V _f were used to reinforce the alloy. The composites were fabricated via a double-compaction reaction sintering technique under vacuum at a compaction pressure of 250 MPa and sintering temperature of 600 °C. At more than 35% burn-off of the carbon chars at the temperature of activation, 915 °C, the total surface area remained virtually unaffected. The ultimate tensile strength and hardness decreased by 23% and 6 %, respectively; with increasing surface area of the reinforcement from 123 to 821 m²g⁻¹. The yield strength and the percentage of elongation decreased by a factor of 2 and 5, respectively. No significant change in sliding wear rate was observed but the coefficient of friction increased by 13 % (0.61 to 0.69). The coefficient of linear thermal expansion was reduced by 16 % (11.7 × 10⁻⁶ to 9.8 × 10⁻⁶ °C⁻¹), and remained unaffected at more than 35 % burn-off. Energy-dispersive spectrometry of the particles of the activated chars showed that oxides of potassium and copper coated the open surfaces. Failure at the matrix-char interface was observed, and this was attributed to localized presence of oxides at the interfaces as identified by electron probe microanalysis. Poor wetting of the oxides by magnesium at the sintering conditions resulted in formation of weak matrix-char interface bonds. J.U. Ejiofor, formerly of the Department of Metallurgical and Materials Engineering, The University of Alabama     

Influence of soil density on gas permeability and water retention in soils amended with in-house produced biochar

Biochar has been used as an environment-friendly enhancer to improve the hydraulic properties(e.g.suction and water retention) of soil.However,variations in densities alter the properties of the soil-biochar mix.Such density variations are observed in agriculture(loosely compacted) and engineering(densely compacted) applications.The influence of biochar amendment on gas permeability of soil has been barely investigated,especially for soil with diffe rent densities.The maj or obj ective of this study is to investigate the water retention capacity,and gas permeability of biochar-amended soil(BAS) with different biochar contents under varying degree of compaction(DOC) conditions.In-house produced novel biochar was mixed with the soil at different amendment rates(i.e.biochar contents of 0%,5% and 10%).All BAS samples were compacted at three DOCs(65%,80% and 95%) in polyvinyl chloride(PVC)tubes.Each soil column was subjected to drying-wetting cycles,during which soil suction,water content,and gas permeability were measured.A simplified theoretical framework for estimating the void ratio of BAS was proposed.The experimental results reveal that the addition of biochar significantly decreased gas permeability k_g as compared with that of bare soil(BS).However,the addition of 5%biochar is found to be optimum in decreasing kg with an increase of DOC(i.e.k_(g,65%) k_(g,80%) k_(g,95%)) at a relatively low suction range(200 kPa) because both biochar and compaction treatment reduce the connected pores.     

Conjugate natural convection heat transfer in an inclined square cavity containing a conducting block

The present work is concerned with computation of natural convection flow in a square enclosure with a centered internal conducting square block both of which are given an inclination angle. Finite volume method through the concepts of staggered grid and SIMPLE algorithm have been applied. Deferred QUICK scheme has been used to discretize the convective fluxes and central difference for diffusive fluxes. The problem of conjugate natural convection has been taken up for validating the code. The abrupt variation in the properties at the solid/fluid interface are taken care of with the harmonic mean formulation. Solution has been performed in the computational domain as a whole with proper treatment at the solid/fluid interface. Computations have been performed for Ra = 10³–10⁶, angle of inclination varying from 15° to 90° in steps of 15° and ratio of solid to fluid thermal conductivities of 0.2 and 5.0. Results are presented in terms of streamlines, isotherms, local and average Nusselt number.