Experimental assessment of drag reduction by traveling waves in a turbulent pipe flow

We experimentally assess the capabilities of an active, open-loop technique for drag reduction in turbulent wall flows recently introduced by Quadrio et al. [J. Fluid Mech., v.627, 161, (2009)]. The technique consists in generating streamwise-modulated waves of spanwise velocity at the wall, that travel in the streamwise direction. A proof-of-principle experiment has been devised to measure the reduction of turbulent friction in a pipe flow, in which the wall is subdivided into thin slabs that rotate independently in the azimuthal direction. Different speeds of nearby slabs provide, although in a discrete setting, the desired streamwise variation of transverse velocity. Our experiment confirms the available DNS results, and in particular demonstrates the possibility of achieving large reductions of friction in the turbulent regime. Reductions up to 33% are obtained for slowly forward-traveling waves; backward-traveling waves invariably yield drag reduction, whereas a substantial drop of drag reduction occurs for waves traveling forward with a phase speed comparable to the convection speed of near-wall turbulent structures. A Fourier analysis is employed to show that the first harmonics introduced by the discrete spatial waveform that approximates the sinusoidal wave are responsible for significant effects that are indeed observed in the experimental measurements. Practical issues related to the physical implementation of this control scheme and its energetic efficiency are briefly discussed.Comment: Article accepted by Phys. Fluids. After it is published, it will be found at http://pof.aip.or

Xylanase production by Aspergillus niger ANL 301 using agro - wastes

Xylanase production by wild-type Aspergillus niger ANL301, newly isolated from wood-waste, was monitored at 24 h intervals for a period 168 h in media containing different carbon sources. The carbon sources were oat-spelt xylan (Fluka) and three agro-wastes (sawdust, sugarcane pulp and wheat bran). Highest xylanase activity of 6.47 units/mL was obtained at 96 h in media containing wheat bran as sole carbon source. Maximum activity value for the media containing sugarcane pulp was 0.95 units/mL obtained also at 96 h. Sawdust and oat spelt xylan gave the peak enzyme activities of 0.65 and 0.80 units/mL respectively at 120 h. High protein yield was obtained in media containing the agro-wastes, with wheat bran giving the highest value of 1.14 mg/mL at 96 h. The maximum specific xylanase activities were 3.86, 3.37, 5.69, and 9.36 units/ mg protein for sawdust, sugarcane pulp, wheat bran and oat spelt xylan, respectively. Out of the three agro-wastes used in this study, wheat bran holds greatest promise for low cost production of the xylanase enzyme

Agro-waste: a potential fermentation substrate for Penicillium chrysogenum

Common agro-wastes found in Lagos, Nigeria (cassava shavings, corncob, sawdust, and sugarcane pulp) were compared with glucose and lactose as fermentation substrates for Penicillium chrysogenum PCL501. Cassava shavings significantly (P<0.001) produced the highest amount of mycelia weight (0.43 ± 0.02 mg/ml) than all the other substrates. This was followed by corncob with peak mycelia weight of 0.33 ± 0.02 mg/ml. Peak mycelia weight of 0.27 ± 0.01 mg/ml was equally obtained with glucose and sugarcane pulp whereas lactose gave a slightly lower peak of 0.25 ± 0.01 mg/ml. Sawdust gave the least mycelia weight of 0.13 ± 0.01 mg/ml. Total sugar content of all the culture media steadily decreased as fungal growth progressed indicating that the organism utilized carbohydrates for growth and mycelia formation. Cultures containing cassava shavings and sawdust gave high protein peaks of 0.84 ± 0.05 and 0.65 ± 0.03 mg/ml respectively. Cultures containing corncob, glucose, lactose and sugarcane pulp yielded lower protein peaks of 0.37 ± 0.02, 0.30 ± 0.02, 0.24 ± 0.02 and 0.18 ± 0.01 mg/ml respectively. The results suggest that cassava shavings, corncob and sugarcane pulp could serve as cheap fermentation substrates for the growth of the fungus. Of all the substrates investigated, cassava shavings have the best potential to serve as substrate for fermentation by Penicillium chrysogenum PCL501. © 2009 International Formulae Group. All rights reserved

Ferromagnetic relaxation by magnon-induced currents

A theory for calculating spin wave relaxation times based on the magnon-electron interaction is developed. The theory incorporates a thin film geometry and is valid for a large range of magnon frequencies and wave vectors. For high conductivity metals such as permalloy, the wave vector dependent damping constant approaches values as high as 0.2, showing the large magnitude of the effect, and can dominate experimentally observed relaxation.Comment: 5 pages, 4 figure

Xylanase production by Penicillium chrysogenum (PCL501) fermented on cellulosic wastes

Xylanase production by Penicillium chrysogenum PCL501, newly isolated from wood-wastes, was monitored at 24 h intervals for a period 168 h in media containing four different carbon sources (oatspelt xylan, wheat bran, sawdust, and sugarcane pulp). The highest xylanase activity of 6.47 Units mL-1 was obtained at 96 h in media containing wheat bran whereas media containing sugarcane pulp gave a peak value of 1.39 Units mL-1 at 144 h. Sawdust and xylan gave a peak xylanase activity of 1.35 and 0.79 Units mL-1 respectively at 120 h. Maximum protein released in xylan-containing media was 0.38 mg mL-1. Higher protein yield was obtained in media containing the agro-wastes, with wheat bran giving the highest value of 1.14 mg mL-1. The maximum specific xylanase activities were 2.59, 8.52, 16.06, and 9.36 Units mg Protein -1 for sawdust, sugarcane pulp, wheat bran and xylan respectively. Out of the three agro-wastes used in this study, wheat bran holds the greatest promise for cost-effective production of the xylanase enzyme. The carbon source is the highest inducer of the enzyme in the fungus

Plant Waste Hydrolysis by Extracellular Enzymes of Aspergillus niger and Penicillium chrysogenum: Effect of Ammonia Pretreatment

Aspergillus niger (ANL301) and Penicillium chrysogenum (PCL 501) cultured in basal media with cellulose as sole carbon source yielded extracellular enzymes which partially hydrolyzed sawdust and sugarcane pulp into simple sugars. Pre-treatment of sawdust by ammonium hydroxide steeping increased the yield of simple sugars. The reducing sugars released from the pretreated sawdust by the crude enzymes of A. niger (ANL301) and P. chrysogenum (PCL 501) were 3.58% and 7.02% of the total hydrolysable sugars respectively. This is in contrast to the 0.92% and 1.02% of the total hydrolysable sugars released respectively by the enzymes of A. niger (ANL301) and P. chrysogenum (PCL 501) from the non-pretreated sawdust. Enzymatic hydrolysis of sugarcane pulp by the crude enzymes was not significantly affected by ammonia pre-treatment. Reducing sugars released from non-pretreated sugarcane pulp by the crude enzymes of A. niger (ANL301) and P. chrysogenum (PCL 501) were respectively 4.17% and 5.08% of the total hydrolysable sugars

Effect of carbon sources on cellulase (EC 3. 2. 1. 4) production by Penicillium chrysogenum PCL501

The effects of glucose, crystalline cellulose and sawdust of Mitragyna cilata on the growth and cellulase production, inferred from cellulase (EC 3. 2. 1. 4) activity, of Penicillium chrysogenum PCL501 was determined. Glucose-containing media gave the highest mycelia weight of 1.78 mg mL-1 in 120 h of incubation. This is about 3.5 – 4.5 times the maximum weights of 0.51 and 0.40 mg mL-1 respectively obtained from the cultures containing cellulose and sawdust. The cultures containing crystalline cellulose and sawdust produced extracellular protein with cellulase (EC 3. 2. 1. 4) activity whereas glucose-containing cultures yielded very low protein and no significant cellulase activity. Maximum protein content of 0.02, 0.13 and 0.46 mg mL-1 respectively were obtained from the cultures containing glucose, cellulose and sawdust. Peak cellulase activity values of 100.0 and 92.2 Units L-1 respectively were obtained for the cultures containing cellulose and sawdust. There is a correlation between the protein released and cellulase activity of the culture filtrates. P. chrysogenum PCL501 produces extracellular proteins with significant cellulase activity in media containing cellulose and sawdust but not in glucose-containing medium. Sawdust is indicated as a good inducer of cellulase activity in the organism. The waste cellulosic material can be used as low-cost carbon source for commercial cellulase production

Penicillin Production by Penicillium Chrysogenum PCL 501: Effect of UV Induced Mutation

Penicillin production by Penicillium chrysogenum (PCL501) fermented on glucose, lactose and four agro-wastes (cassava shavings, corncob, sawdust, and sugarcane pulp) was monitored with HPLC. The highest amount of penicillin was obtained with sugarcane pulp. Penicillin yield from a 7-day culture of the fungus was 8.65 ± 0.05, 7.68 ± 0.03, 6.85 ± 0.05, 5.54 ± 0.01, 5.32 ± 0.05 and 2.23 ± 0.02μg/ml respectively on sugarcane pulp, glucose, cassava shavings, corncob, lactose, and sawdust. Two mutant strains, UVP1 and UVP2, were obtained by exposing the wild strain (PCL501) to ultraviolet irradiation for 20 and 25 minutes respectively. The 7-day culture of UVP1 and UVP2 on sugarcane pulp yielded 14.83 ± 0.05 and 14.97 ± 0.05 μg/ml penicillin respectively. This represented over 70% increase in penicillin production over the parent strain. There is a good prospect of producing cheaper and effective penicillin using the mutant strains of P. chrysogenum an

Screening and characterisation of CdTe/CdS quantum dot-binding peptides for material surface functionalisation

Quantum dots (QDs) are promising nanomaterials due to their unique photophysical properties. For them to be useful in biological applications, the particle surface generally needs to be conjugated to biological molecules, such as antibodies. In this study, we screened CdTe/CdS QD-binding peptides from a phage display library as linkers for simple and bio-friendly QD modification. Among five QD-binding peptide candidates, a series of truncated peptides designed from two high-affinity peptides were subjected to an array-based binding assay with QDs to assess their functional core sequences and characteristics. Linking these isolated, shortened peptides (PWSLNR and SGVYK) with an antibody-binding peptide (NKFRGKYK) created dual-functional peptides that are capable of QD surface functionalisation by antibodies. Consequently, the dual-functional peptides could mediate anti-CD9 antibody functionalisation onto CdTe/CdS QD surface; CD9 protein imaging of cancer cells was also demonstrated. Our proposed peptides offer an effective vehicle for QD surface functionalisation in biological applications