Rev Min Research Articles

A comprehensive study of atmospheric pressure leaching of saprolitic laterites in acidic media

The mineralogy of saprolitic laterites has been characterised using X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis and X-ray fluorescence. The results showed that the ore consists mainly of nickel- and iron-substituted lizardite and minor quantities of magnetite. Several experiments were conducted to investigate the extraction of nickel and cobalt from lizardite at atmospheric pressure in acidic media as a function of particle size, sulphuric acid concentration, reaction time, temperature and liquid to solid ratio. Generally, as much as 69·6%Ni and 30·8%Co were extracted under the experimental condition of 10% (v/v) H2SO4, reaction temperature 90°C, reaction time 2 h, particle size 59·9% passing through 74 μm, stirring at 500 rev min–1 and liquid to solid ratio 3 mL g–1. Increased extraction of Ni and Co from lizardite with sulphuric acid could be obtained by introducing leaching additives such as ferric chloride (Ni leaching rate 74·8%, Co leaching rate 45·4%), organic acid (Ni leaching rate 76·3%, Co leaching rate 48·7%) and fluoride (Ni leaching rate 81·7%, Co leaching rate 52·3%).

Regulation of tacrolimus production by altering primary source of carbons and amino acids

In the present communication, attempts have been made to regulate the tacrolimus production by supplementing commercial source of carbons and amino acids timely. Tacrolimus production was regulated by supplying vegetable oils and amino acids, individually and in combination. Tacrolimus quantification was done by HPLC. Streptomyces spp. MA6858 B3178 was found to produce 115.3 mg l(-1) of tacrolimus. The rotation speed of shake flask, pH of the broth and supply of air were maintained at 7.1, 230 rev min(-1) and 2.0 vv m air respectively. The effect of carbons on tacrolimus production was noticed to be of diphasic manner. During the first 24 h of culture, monosaccharide is used for the growth of microbe. However, after the lapse of 36 h, addition of soya oil and l-lysine in combination enhanced the tacrolimus production to 115.3 mg l(-1). Besides this, pH of broth was also noticed as a critical factor in monitoring tacrolimus biosynthesis. The newly isolated mutant Streptomyces spp. MA6858 B3178 having high potential for tacrolimus production as compared to existing data can be well used for the commercialization of tacrolimus.

Conversion of volatile fatty acids into polyhydroxyalkanoate byRalstonia eutropha

The aims of this study were to optimize condensed corn solubles (CCS) as a medium for growth of Ralstonia eutropha and to determine the effects of individual volatile fatty acids (VFAs) on polyhydroxyalkanoate (PHA) production. A CCS medium of concentration 240 g l(-1) with a carbon : nitrogen ratio of 50 : 1 was developed as the optimal medium. Cultures were grown in 1-l aerated flasks at 250 rev min(-1) at 30 degrees C for 120 h. Comparable growth rates were observed in CCS vs a defined medium. At 48 h, VFAs were fed individually at different levels. Optimal levels of all the acids were determined to maximize PHA production. An overall comparison of the VFAs indicated that butyric and propionic acids provided the best results. An optimized CCS medium supported growth of R. eutropha. Butyric and propionic acids were the most efficient carbon sources to maximize PHA production when added at the 5 g l(-1) level. The study shows that a byproduct of ethanol industry can be effectively used as a low cost medium for PHA production, thus partly reducing the cost of commercialization of biopolymers.

Meloidogyne chitwoodi and Meloidogyne fallax

<i>Meloidogyne chitwoodi</i> and <i>Meloidogyne fallax</i>

Comparison of the effect of biodiesel-diesel and ethanol-diesel on the gaseous emission of a direct-injection diesel engine

Experiments were conducted on a 4-cylinder direct-injection diesel engine using ultralow sulfur diesel blended with biodiesel and ethanol to investigate the gaseous emissions of the engine under five engine loads at the maximum torque engine speed of 1800 rev min −1. Four biodiesel blended fuels and four ethanol blended fuels with oxygen concentrations of 2%, 4%, 6% and 8% were used. With the increase of oxygen content in the blended fuels, the brake thermal efficiency improves slightly. For the diesel-biodiesel fuels, the brake specific HC and CO emissions decrease while the brake specific NO x and NO 2 emissions increase. The emissions of formaldehyde, 1,3-butadiene, toluene, xylene and overall BTX (benzene, toluene, xylene) in general decrease, however, acetaldehyde and benzene emissions increase. For the diesel-ethanol fuels, the brake specific HC and CO emissions increase significantly at low engine load, NO x emission decreases at low engine load but increases at high engine load. The emissions of benzene and BTX vary with engine load and ethanol content. Similar to the biodiesel-diesel fuels, the formaldehyde, 1,3-butadiene, toluene and xylene emissions decrease while the acetaldehyde and NO 2 emissions increase. Despite having the same oxygen contents in the blended fuels, there are significant differences in the gaseous emissions between the biodiesel-diesel blends and the ethanol-diesel blends.

Characterization of Mechanical Alloying Processed Ti-Si-B Nanocomposite Consolidated by Spark Plasma Sintering

The microstructure and mechanical properties of TiB₂/Si nanocomposites based on the Ti-Si-B system, consolidated by spark plasma sintering of mechanically alloyed activated nanopowders, have been characterized. Mechanical Alloying was carried out in a planetary ball mill for 180 min with 350 rev min?¹. The powders were pressed in vacuum at a pressure of 60 ㎫, generating a maximum temperature in the graphite mould of 1400℃. Analysis of the synthesized nanocomposites by SEM, XRD and TEM showed them to consist of TiB₂ second phase, sub-micron in size, with no third phase. Composites consolidated from powders mechanically alloyed from an initial elemental powder mix of 0.3 mol Si, 0.7 ㏖ Ti, and 2.0 ㏖ B achieved the best relative density (97%) and bending strength (774 ㎫); the highest Vickers hardness of 14.7 ㎬ was achieved for the 0.1-0.9-2.0 mol starting composition.

Heterodera glycines

<i>Heterodera glycines</i>

Friction stir welding of aluminium 7136-T76511 extrusions

This research programme evaluates the as welded properties of Al 7136-T76511 extrusions joined through friction stir welding (FSW). Microstructural characterisation and mechanical testing were performed on the baseline material and on panels friction stir welded at 250 and 350 rev min–1 (all other weld parameters held constant). Transmission electron microscopy revealed the microstructural features in each of the unique weld regions and demonstrated that the precipitate density and morphology in these regions correlates with the temperature profile produced by the FSW process. A thermal model of FSW is developed that utilises an energy based scaling factor to account for tool slip. The slip factor is derived from an empirical relationship between the ratio of the maximum welding temperature to the solidus temperature and energy per unit length of weld. The thermal model successfully predicts the maximum welding temperatures and profiles over a range of energy levels. The mechanical behaviour after welding is correlated to the temperature distribution predicted by the model and to the observed microstructural characteristics. As welded mechanical properties of the alloy trended positively with the energy per unit length of weld, i.e. the highest joint efficiency was achieved at the highest welding temperature.

Fabrication of SiC particle reinforced composite on aluminium surface by friction stir processing

A feasibility investigation has been carried out of the formation of surface composite by uniformly distributing SiC particles 1˙25 µm in size into a surface layer of an A 1050-H24 Al plate through friction stir processing (FSP). The SiC particle was filled into a groove cut on the Al plate, covered by an Al sheet 2 mm thick, and a rotating tool was penetrated from the cover sheet so that the probe tip reached a depth beyond the groove bottom. The effects of process parameters (rotation speed and travelling speed) and applying multiple passes on the distribution of SiC particle in the nugget zone were investigated. The effects of groove size and its position relative to the tool probe were also investigated. Applying multiple passes had a great effect on the homogeneity of the SiC particle distribution. At rotation speeds of 2000–3000 rev min−1, the SiC particles tended to cluster in some places in the nugget zone. By decreasing the rotation speed to 1000–1500 rev min−1, the SiC particle was distributed in almost all the nugget zone area when the groove was 2–3 mm wide and 1˙5 mm deep. On the other hand, the stirring action of FSP was insufficient to distribute homogenously the SiC particles when the groove size was increased to 3×2 mm. By shifting the groove position towards the advancing side of the tool probe, the distribution of the SiC particles in the nugget zone became better. The defect free nugget zone with homogenously distributed SiC particles was obtained in a sample produced by FSP at rotation speeds of 1500 rev min−1 for the first pass and 1250 rev min−1 for the second and third passes. Microhardness of the nugget zone was increased to a level as high as 55 HV when the groove size was 3×1˙5 mm. The effect of the rotation speed on the particles dispersion was discussed with particular reference to the vertical material flow in the nugget zone.

Experimental investigation of regulated and unregulated emissions from a diesel engine fueled with ultralow-sulfur diesel fuel blended with ethanol and dodecanol

Experiments were conducted on a four-cylinder direct-injection diesel engine using ultralow-sulfur diesel as the main fuel, ethanol as the oxygenate additive and dodecanol as the solvent, to investigate the regulated and unregulated emissions of the engine under five engine loads at an engine speed of 1800 rev min −1. Blended fuels containing 6.1%, 12.2%, 18.2% and 24.2% by volume of ethanol, corresponding to 2%, 4%, 6% and 8% by mass of oxygen in the blended fuel, were used. The results indicate that with an increase in ethanol in the fuel, the brake specific fuel consumption becomes higher while there is little change in the brake thermal efficiency. Regarding the regulated emissions, HC and CO increase significantly at low engine load but might decrease at high engine load, NO x emission slightly decreases at low engine load but slightly increases at high engine load, while particulate mass decreases significantly at high engine load. For the unregulated gaseous emissions, unburned ethanol and acetaldehyde increase but formaldehyde, ethene, ethyne, 1,3-butadiene and BTX (benzene, toluene and xylene) in general decrease, especially at high engine load. A diesel oxidation catalyst (DOC) is found to reduce significantly most of the pollutants, including the air toxics.

Modification of culture conditions for production of the anti-tubercular hirsutellones by the insect pathogenic fungusHirsutella niveaBCC 2594

This work aimed to improve the production of anti-tubercular hirsutellones by the insect pathogenic fungus Hirsutella nivea BCC 2594. The fungus was cultivated under different carbon/nitrogen sources and aerations (shake vs static flasks) to improve the production of the anti-tubercular alkaloids, hirsutellones A-D. Under the basal conditions, static cultivation at 25 degrees C in minimum salt medium, only hirsutellone B and C were detected with maximum concentrations of 139.00 and 18.27 mg l(-1). Substitution of fructose for glucose and peptone for yeast extract increased the titres of hirsutellones A, B and C about two- to threefold. However, hirsutellone D was not detected in this medium. Culture agitation induced the production of hirsutellone D. As a result, the significant amounts of hirsutellones A-D were obtained with the concentration of 29.93, 169.63, 22.65 and 15.71 mg l(-1) within 15 days. Improved titres of hirsutellones in H. nivea BCC 2549 were achieved with an agitated (200 rev min(-1)) fructose-peptone medium at 25 degrees C. Improved yields of hirsutellones B-D will enable medicinal chemistry modifications leading to a development of a potential candidate for tuberculosis therapy.

Combustion and emission characteristics of a direct injection, compression‐ignition engine when operated on Honge oil, HOME and blends of HOME and diesel

This paper reports the results of research conducted to study the fuel properties of Honge oil and blends of its ester and the subsequent testing of these oils in a four‐stroke, single cylinder, water‐cooled, direct injection, compression‐ignition (CI) engine. Experiments were conducted with injection timings of 19, 23 and 27° BTDC at various loads and at a constant rated speed of 1500 rev min−1. The performance and emission characteristics of Honge oil and Honge oil methyl ester (HOME) blended with diesel, to produce blends designated B20, B40 and B80, were studied. The heat release rates, maximum rate of pressure rise, ignition delay, and combustion duration for these fuel combinations were determined.

Electrochemistry of tin deposition from mixed sulphate and methanesulphonate electrolyte

The electrodeposition of tin, at a copper surface, from a tin sulphate (0˙014 mol dm–3) electrolyte containing methanesulphonic acid (12 ˙5 vol.-%) at 295 K has been studied. Cyclic voltammetry, using potential sweep rates of 8–128 mV s–1, at a stationary copper electrode provided information on the potential ranges for tin deposition and stripping. Linear sweep voltammetry, at a copper rotating disc electrode was used to evaluate the mass transport characteristics of the system under controlled, laminar flow conditions. The changes in the limiting current density with a Sn2+ concentration of 0˙006–0˙078 mol dm–3 and an electrode rotation rate of 200–4800 rev min–1 were quantified. Randles-Sevčik and Levich equations were used to give an averaged diffusion coefficient for Sn2+ of 5˙4 × 10–6 cm2 s–1.

Role of casein on induction and enhancement of production of a bacterial milk clotting protease from an indigenously isolated Bacillus subtilis

To isolate and enhance the yield of a bacterial milk clotting protease (MCP) through process optimization and scale up. Bacillus subtilis was isolated as MCP producer with good milk clotting activity (MCA) per proteolytic activity (PA) index. The enzyme production was inducible with casein and enhanced with fructose and ammonium nitrate resulting in 571.43 U ml(-1) of enzyme. Medium containing 4% fructose, 0.75% casein, 0.3% NH(4)NO(3) and 10 mmol l(-1) CaCl(2), pH 6.0, inoculated with 4% (v/v) inoculum, incubated at 37 degrees C, 200 rev min(-1) for 72 h gave maximum production. A 6.67-fold increase in MCP yield with very high MCA per PA index was observed after final optimization indicating similarity to rennets. Mostly fungal MCPs have been reported. The MCA and MCA per PA index of this bacterium is comparable to that of many fungal reports and better than quite a few bacterial MCPs. Thus, this enzyme by B. subtilis has good probability of successful use in cheese production.

A sensitive determination method for carbendazim and thiabendazole in apples by solid-phase microextraction−high performance liquid chromatography with fluorescence detection

A new analytical method for the determination of carbendazim (MBC) and thiabendazole (TBZ) in apples is reported, based on solid-phase microextraction (SPME) coupling HPLC with fluorescence detection. The main SPME and HPLC experimental conditions were optimized. The apples were first blended and centrifuged. Then, an aliquot of the resulting solution was subjected to SPME on a 60 µm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre for 35 min at room temperature with the solution being stirred at 1100 rev min–1. The extracted pesticides on the SPME fibre were desorbed in the mobile phase into the SPME/HPLC interface for HPLC analysis. The method was linear over the range 0.01–1 mg kg–1 in apples for both MBC and TBZ, with detection limits of 0.005 and 0.003 mg kg–1 and correlation coefficients of 0.9995 and 0.9998, respectively. The average recoveries for MBC and TBZ were 91.5 and 92.3% with the relative standard deviations (RSD) of 4.7 and 4.1% at the 0.1 mg kg–1 level, and 94.6 and 96.1% with RSD of 3.3 and 3.8% at the 0.5 mg kg–1 level, respectively. The method is simple, sensitive, organic solvent-free and is suitable for the determination of MBC and TBZ in apples.

The role of the slope of oxygen consumption and EMG activity on freely chosen pedal rate selection

The objective of this study was to verify the following hypothesis: the pedal rate that minimizes root mean square (RMS) slope and the slow component amplitude of oxygen consumption could be close to the freely chosen pedal rate (FCPR) used by well-trained cyclists. Nine male competitive cyclists performed a 21 min submaximal exercise on a cycle ergometer at a workload of 65% of their respective peak aerobic power. For each session, the subject's pedal rate was freely chosen or assigned to 60, 75, 90 or 105 rev min(-1). When pedal rates were imposed, the electromyographic root mean square slope, the oxygen uptake during the third minute and the 20th min, and the slow component amplitude of oxygen consumption were used in the analysis. In order to determine the optimal pedal rate (OPR), a quadratic function was fitted to the data by regression, for each variable measured. The mean values of OPR relative to oxygen uptake during the third min (71+/-9 rev min(-1)) were lower than the mean values of the OPR relative to the slow component amplitude of oxygen consumption (82+/-8 rev min(-1)), the electromyographic root mean square slope (80+/-7 rev min(-1)) and freely chosen pedal rate (86+/-13 rev min(-1)). Freely chosen pedal rate was not significantly different from the OPR in reference to the amplitude of the slow component of oxygen consumption, electromyographic root mean square slope, and oxygen uptake during the 20th min. OPR for RMS slope was correlated (R=0.72) to FCPR. Expert cyclists were likely to use a spontaneous pedal rate that minimizes neuromuscular fatigue.

Effect of pedaling rates and myosin heavy chain composition in the vastus lateralis muscle on the power generating capability during incremental cycling in humans

In this study, we have determined power output reached at maximal oxygen uptake during incremental cycling exercise (P(I, max)) performed at low and at high pedaling rates in nineteen untrained men with various myosin heavy chain composition (MyHC) in the vastus lateralis muscle. On separate days, subjects performed two incremental exercise tests until exhaustion at 60 rev min(-1) and at 120 rev min(-1). In the studied group of subjects P(I, max) reached during cycling at 60 rev min(-1) was significantly higher (p=0.0001) than that at 120 rev min(-1) (287+/-29 vs. 215+/-42 W, respectively for 60 and 120 rev min(-1)). For further comparisons, two groups of subjects (n=6, each) were selected according to MyHC composition in the vastus lateralis muscle: group H with higher MyHC II content (56.8+/-2.79 %) and group L with lower MyHC II content in this muscle (28.6+/-5.8 %). P(I, max) reached during cycling performed at 60 rev min(-1) in group H was significantly lower than in group L (p=0.03). However, during cycling at 120 rev min(-1), there was no significant difference in P(I, max) reached by both groups of subjects (p=0.38). Moreover, oxygen uptake (VO(2)), blood hydrogen ion [H(+)], plasma lactate [La(-)] and ammonia [NH(3)] concentrations determined at the four highest power outputs completed during the incremental cycling performed at 60 as well as 120 rev min(-1), in the group H were significantly higher than in group L. We have concluded that during an incremental exercise performed at low pedaling rates the subjects with lower content of MyHC II in the vastus lateralis muscle possess greater power generating capabilities than the subjects with higher content of MyHC II. Surprisingly, at high pedaling rate, power generating capabilities in the subjects with higher MyHC II content in the vastus lateralis muscle did not differ from those found in the subjects with lower content of MyHC II in this muscle, despite higher blood [H(+)], [La(-)] and [NH(3)] concentrations. This indicates that at high pedaling rates the subjects with higher percentage of MyHC II in the vastus lateralis muscle perform relatively better than the subjects with lower percentage of MyHC II in this muscle.

Effect of cultivation conditions on spore production from Bacillus amyloliquefaciens B128 and its antagonism to Botrytis elliptica

To maximize spore production by Bacillus amyloliquefaciens B128, and its antagonism to the fungal pathogen Botrytis elliptica B061. In the 5-l stirred-tank bioreactor (STR), with the 0.5 vvm aeration rate, an agitation rate of 200 rev min(-1) significantly enhanced the spore yield compared to the same in 300 rev min(-1) cultivations. In a 20-l airlift bioreactor (ALR) the maximal spore production was further increased with a controlled aeration rate of 2.5 vvm operated in a 24-mesh net-draft tube mode, and no pH control cultivation. This spore yield in the 20-l ALR was five- and eightfold higher; in addition the cultivation period was 19 h shorter, compared to that obtained from shaker flask and in the 5-l STR cultivations respectively. Although culture conditions are still to be optimized, by using an ALR with net-draft tube, a scaling up from shaker flasks and STR to ALR of spore production by the strain B128 is technically feasible. The spore yields obtained using bioreactors were much higher than those previously reported. The freshly produced spore preparations from the B128 strain significantly antagonized the grey mould pathogen B. elliptica.

Optimization of fermentation condition for antibiotic production by Xenorhabdus nematophila with response surface methodology

To evaluate the influence of environmental parameters on the production of antibiotics (xenocoumacins and nematophin) by Xenorhabdus nematophila and enhance the antibiotic activity. Response surface methodology (RSM) was employed to study the effects of five parameters (the initial pH, medium volume in flask, rotary speed, temperature and inoculation volume) on the production of antibiotics in flask cultures by X. nematophila YL001. A 2(5-1)-factorial central composite design was chosen to explain the combined effects of the five parameters and to design a minimum number of experiments. The experimental results and software-predicted values of production of antibiotics were comparable. The statistical analysis of the results showed that, in the range studied, medium volume in flask, rotary speed, temperature and inoculation volume had a significant effect (P < 0.05) on the production of antibiotics at their individual level, medium volume in flask and rotary speed showed a significant influence at interactive level and were most significant at individual level. The maximum antibiotic activity was achieved at the initial pH 7.64, medium volume in 250 ml flask 25 ml, rotary speed of 220 rev min(-1), temperature 27.8 degrees C and inoculation volume of 15.0%. Maximum antibiotic activity of 331.7 U ml(-1) was achieved under the optimized condition. As far as known, there are no reports of production of antibiotic from X. nematophila by engineering the condition of fermentation using RSM. The results strongly support the use of RSM for fermentation condition optimization. The optimization of the environmental parameters resulted not only in a 43.4% higher antibiotic activity than unoptimized conditions but also in a reduced amount of the experiments. The chosen method of optimization of fermentation condition was efficient, relatively simple and time and material saving. This study should contribute towards improving the antibiotics activity of X. nematophila. Integrated into a broader study of the impact of environmental factors on the production of antibiotic, this work should help to build more rational control strategy, possibly involving scale-up of production of antibiotics by X. nematophila.

The influence of crank length and cadence on mechanical efficiency in hand cycling

The purpose of this study was to determine the effect of crank length and cadence on mechanical efficiency in hand cycling. Eight wheelchair dependent, high performance athletes completed four 4-min submaximal exercise bouts at a constant power output of 90 W over the different experimental conditions (crank length, pedal rate) using a sports hand bike (Draft, Godmanchester, UK). Two different crank lengths (180 and 220 mm) were tested at two different cadences (70 and 85 rev min(-1)) using the synchronous mode of cranking. Physiological measures of oxygen uptake (VO2) minute ventilation, blood lactate (B[La]), heart rate (HR), rate of perceived exertion (RPE) were recorded, gross (GE) and net (NE) efficiency were calculated. A two-way ANOVA with repeated measures was applied to determine the effects of crank length, cadence and their interaction on these physiological measures. Both GE and NE were significantly higher and V(O)(2) significantly lower for the 180 mm crank (P < 0.05). No significant main effect was found for cadence on the physiological measures (P > 0.05). Likewise, no interactions between crank length and pedal rate were found. There was however, a trend observed with HR and B[La] often lower with the 180 mm crank, indicating lower physiological stress. The RPE data supported this finding, with a tendency for lower ratings with the 180 mm crank (9 +/- 2 vs. 10 +/- 3). The short crank length when used at 85 rev min(-1) was found to be the most efficient (GE 21.4 +/- 3.1%). In conclusion, crank length has a significant effect on ME in hand cycling. A shorter crank length of 180 mm was found to be more efficient than the 220 mm, regardless of pedal rate during hand cycling.