Feeding Strategies of Two-Stage Fed-Batch Cultivation Processes for Microbial Lipid Production from Sugarcane Top Hydrolysate and Crude Glycerol by the Oleaginous Red Yeast Rhodosporidiobolus fluvialis

Microbial lipids are able to produce from various raw materials including lignocellulosic biomass by the effective oleaginous microorganisms using different cultivation processes. This study aimed to enhance microbial lipid production from the low-cost substrates namely sugarcane top hydrolysate and crude glycerol by Rhodosporidiobolus fluvialis DMKU-SP314, using two-stage fed-batch cultivation with different feeding strategies in a 3 L stirred-tank fermenter. The effect of two feeding strategies of 147.5 g/L crude glycerol solution was evaluated including pulse feeding at different starting time points (48, 24, and 72 h after initiation of batch operation) and constant feeding at different dilution rates (0.012, 0.020, and 0.033 h−1). The maximum lipid concentration of 23.6 g/L and cell mass of 38.5 g/L were achieved when constant feeding was performed at the dilution rate of 0.012 h−1 after 48 h of batch operation, which represented 1.24-fold and 1.27-fold improvements in the lipid and cell mass concentration, respectively. Whereas, batch cultivation provided 19.1 g/L of lipids and 30.3 g/L of cell mass. The overall lipid productivity increased to 98.4 mg/L/d in the two-stage fed-batch cultivation. This demonstrated that the two-stage fed-batch cultivation with constant feeding strategy has the possibility to apply for large-scale production of lipids by yeast.

Species richness and vulnerability to disturbance propagation in real food webs

A central issue in ecology is understanding how complex and biodiverse food webs persist in the face of disturbance, and which structural properties affect disturbance propagation among species. However, our comprehension of assemblage mechanisms and disturbance propagation in food webs is limited by the multitude of stressors affecting ecosystems, impairing ecosystem management. By analysing directional food web components connecting species along food chains, we show that increasing species richness and constant feeding linkage density promote the establishment of predictable food web structures, in which the proportion of species co-present in one or more food chains is lower than what would be expected by chance. This reduces the intrinsic vulnerability of real food webs to disturbance propagation in comparison to random webs, and suggests that biodiversity conservation efforts should also increase the potential of ecological communities to buffer top-down and bottom-up disturbance in ecosystems. The food web patterns observed here have not been noticed before, and could also be explored in non-natural networks.

Analysis Of The Effect Of Slope Of The Scratch Side Angle Through The Post Tool On Surface Level Surface At The Working Tool Stermination ST 37

The purpose of this research is to see the effect of slope of incision angle chisel through Tool Post to roughness of surface of object. The method used is a lathe ST 37, with 0.5 mm cutting depth, with side angle cutting angle by tilting the Post Tool, ie: 10˚ tilted to the left, 10˚ tilted right, 0˚ (perpendicular), 5˚ tilted right, and 5˚ tilted left. Feeding (constant feeding) is: 0.281 mm / rotation, main cutting corner of chisel 80˚ and cutting speed = 740 rpm. Then the workpiece measured the surface roughness by using Surface Tester Mitutoyo SJ-201P. The result showed that, the smallest surface roughness rate achieved was (ΣRap) = 7, 42 μm with N9 surface roughness class with the Post Tool angle 5 ° to the left. While the largest surface roughness rate achieved is (ΣRap) = 13, 76 μm with the surface roughness class N11 with the tool angle post 10 ° to the right. The value of the roughness level achieved is between N9 - N11.

Experimental observations on sorting patterns of heterogeneous sediment mixtures in low constrained flows

Field and laboratory investigations indicate that gravel bed rivers with bimodal grain size distribution and low lateral confinement, such as in the case of braided or multi-channel rivers, can present simultaneously active channel variations, both in the planimetric and altimetric directions, together with planimetric and vertical sorting. Such aspects were reproduced in new flume experiments considering three flow confinements with characteristic aspect ratios from about 80 to 5. Three long runs of about 60 hours were carried out under constant feeding rate conditions, with a bimodal mixture of natural sediments, a fixed flume slope of 3.18 %, and width imposed by lateral walls from 0.50 m to 0.12 m. We present here the results obtained with the first run, with a width of 0.5 m. We observed fluctuations of bed surface granulometric composition, bed slope, and outlet solid discharge; each of which with its own periodicity. In particular, the rearrangement of the bed surface texture was rapid. Cyclic bed states were observed: a stage of coarsening and aggradation corresponding to low values of outlet solid discharge; a stage of fining and degradation concomitant to high values of transport rate. The other two on-going runs (narrower configurations) aim at investigate the effect of lateral confinement on the morphodynamics of the system.

Blockage mechanism of metal wire in semi-dieless drawing and stable forming method

Blockage easily happens during semi-dieless drawing, in which die drawing follows dieless drawings, under constant feeding speed mode. In this paper, the blockage mechanism is first studied, and then variable feeding speed mode is proposed to solve the problem. Experiments of semi-dieless drawing under the constant and the variable feeding speed modes are performed at different area reduction of die drawing, while the total area reductions are kept the same as 33%. Variation of wire diameter at die entry is measured. Results show that the area reduction of die drawing increases gradually, in the meanwhile that of dieless drawing decreases gradually under the constant feeding speed mode. This could result in formation of multiple transition sections of wire diameter, the number of which depends on the area reduction of die drawing. Eventually, semi-dieless drawing deteriorates into die drawing, resulting in the blockage when the area reduction exceeds equipment's capacity. The variable feeding speed mode only allows the formation of one transition section, which avoids the blockage. Continuous and stable semi-dieless drawing with 33% total area reduction is realized under the variable feeding speed mode.

Research on Uniform Surface Roughness in Grinding of Revolving Curved Surface

When grinding the revolving curved surface with Arc Envelope Grinding Method, the different curvatures in the convex and concave surfaces make a great difference in the surface roughness. In order to solve this problem, the relationship among envelope height, feeding rate, rotational speed and curvature of workpiece was analyzed based on equal-envelope-height grinding method. The results presented that, low feeding rate of grinding wheel and high rotational speed of workpiece were helpful to obtain smaller envelope height. And the smaller the radius of workpiece curvature, the more different the surface roughness. Besides, it was an effective method to solve this problem by changing feeding rate. The feeding rate should be changed directly proportionally to radius of workpiece curvature. Then, the experimental results indicate that, the fluctuation ratio of surface roughness with variable feeding rate is reduced to 4.896% from 26.17% with constant feeding rate. It proves the validity of hypothesis.

Copepod flow modes and modulation: a modelling study of the water currents produced by an unsteadily swimming copepod

Video observation has shown that feeding-current-producing calanoid copepods modulate their feeding currents by displaying a sequence of different swimming behaviours during a time period of up to tens of seconds. In order to understand the feeding-current modulation process, we numerically modelled the steady feeding currents for different modes of observed copepod motion behaviours (i.e. free sinking, partial sinking, hovering, vertical swimming upward and horizontal swimming backward or forward). Based on observational data, we also reproduced numerically a modulated feeding current associated with an unsteadily swimming copepod. We found that: (i) by changing its propulsive force, a copepod can switch between different swimming behaviours, leading to completely different flow-field patterns in self-generated surrounding flow; (ii) by exerting a time-varying propulsive force, a copepod can modulate temporally the basic flow modes to create an unsteady feeding current which manipulates precisely the trajectories of entrained food particles over a long time period; (iii) the modulation process may be energetically more efficient than exerting a constant propulsive force onto water to create a constant feeding current of a wider entrainment range. A probable reason is that the modulated unsteady flow entrains those water parcels containing food particles and leaves behind those without valuable food in them.

High Doped p-Type GaN Grown by Alternative Co-Doping Technique

We investigated the electrical properties of Mg-doped GaN grown by alternative pulse supplies of source and dopant materials in metalorganic vapor phase epitaxy. We obtained the hole concentration of 6×1018cm-3 for p-type GaN grown on a sapphire substrate by repetition of supply and purging of Ga and Mg sources in the constant NH3 flow, while that of p-type GaN grown by the constant feeding of Ga and Mg sources was 2×1018cm-3. By using alternative feedings of Ga source and NH3 with Mg-Si co-doping, we obtained a highly hole concentration of 2×1019cm-3 for p-type GaN which was grown directly on a low temperature AlN buffer layer. We also obtained the hole concentration of 6×1018cm-3 for p-type GaN which was grown on an AlGaN layer on a SiC substrate by alternative co-doping technique. The activation energies for Mg-doped GaN grown by the pulse feedings of source materials were lower than that for GaN grown by continuous supplies of source materials as used in the conventional technique.