Photofermentative hydrogen production from molasses: Scale-up and outdoor operation at low carbon-to-nitrogen ratio

Photofermentative hydrogen production was carried out under outdoor conditions with a Rhodobacter capsulatus strain on molasses, a renewable and sustainable feedstock. An existing photobioreactor design was scaled-up from 9 L to 20 L. The decreased carbon-to-nitrogen (C/N) ratio of 13.0, compared to our previous work, accelerated growth and resulted in a reduced lag period for hydrogen production as well as higher productivities in the exponential phase. However, the low C/N ratio also promoted a high optical density due to growth, limiting light transmission. Still, the maximum productivity was found as 0.47 mol H₂/(m³·h), significantly higher than our result with the smaller reactor volume. High rates of production could not be maintained presumably due to the combined effects of cloudy periods, the aforementioned C/N ratio and decreasing pH. These results suggest that the scale-up was successful and there is potential for further improvement using optimal C/N ratio and cell concentration values.     

Fatigue damage in composite cylinders

In this study, optimal angle‐ply orientation of symmetric composite cylinders under fatigue loading is investigated. The fiber‐reinforced plastic cylinders were manufactured from E‐glass/epoxy. The layers were manufactured symmetrically in [±75°]₂, [±60°]₂, [±55°]₂, and [±45°]₂ orientations. Burst pressure of filament‐wound composite cylinders under alternating pure internal pressure was measured experimentally. Internal fatigue pressure testing method was applied to the composite cylinders in close‐ended condition. For this study, a PLC controlled hydraulic pressure testing machine has been employed. The static burst pressure values of specimens were measured; subsequently, fatigue test pressure was applied in 70, 60, and 50% stress levels of burst pressure for each orientation. Damage propagations of the composite cylinders on these stress levels were observed as whitening, leakage, and final failure for [±60°]₂, [±55°]₂, and orientations. When the damage propagation of [±75°]₂ angle‐ply cylinder was observed, whitening and leakage did not occur and final failure occurred suddenly. Stress‐cycle curves obtained from the tests are given in graphics. Experimental results reveal that variation in stress levels and the winding angles have considerable effects on final failure cycles, which is also presented graphically. The optimum winding angle for the composite pressure cylinders or vessels under internal fatigue pressure load was obtained as [±45°]₂ orientation. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Effects of Growth Rates and Compositions on Dendrite Arm Spacings in Directionally Solidified Al-Zn Alloys

Dendritic spacing can affect microsegregation profiles and also the formation of secondary phases within interdendritic regions, which influences the mechanical properties of cast structures. To understand dendritic spacings, it is important to understand the effects of growth rate and composition on primary dendrite arm spacing (λ ₁) and secondary dendrite arm spacing (λ ₂). In this study, aluminum alloys with concentrations of (1, 3, and 5 wt pct) Zn were directionally solidified upwards using a Bridgman-type directional solidification apparatus under a constant temperature gradient (10.3 K/mm), resulting in a wide range of growth rates (8.3–165.0 μm/s). Microstructural parameters, λ ₁ and λ ₂ were measured and expressed as functions of growth rate and composition using a linear regression analysis method. The values of λ ₁ and λ ₂ decreased with increasing growth rates. However, the values of λ ₁ increased with increasing concentration of Zn in the Al-Zn alloy, but the values of λ ₂ decreased systematically with an increased Zn concentration. In addition, a transition from a cellular to a dendritic structure was observed at a relatively low growth rate (16.5 μm/s) in this study of binary alloys. The experimental results were compared with predictive theoretical models as well as experimental works for dendritic spacing.     

High‐performance liquid chromatography of some natural dyes: analysis of plant extracts and dyed textiles

In this study, wool fibre samples were mordanted by means of 25% alum mordant solution. The mordanted wool samples were dyed in 50%Reseda luteola L. (weld), 20%Rhamnus petiolaris Boiss (buckthorn) and 50%Datisca cannabina L. (bastard hemp) dyebaths. A reverse‐phase high‐performance liquid chromatography with diode‐array detection method was utilised for the identification of dyes in the dyed wool samples and the plant extracts. The extraction of dyes was carried out with a hydrogen chloride/methanol/water (2:1:1; v/v/v) mixture.     

Elman's recurrent neural network applications to condition monitoring in nuclear power plant and rotating machinery

The purpose of this study is to show the capability of recurrent neural nets (RNN) for condition monitoring and diagnosis in nuclear power plant systems and rotating machinery. In the first application, the study addresses the use of RNN for detecting anomalies introduced from the simulated power operation of a high-temperature gas cooled nuclear reactor. In the second, it is used to detect the motor bearing damage using a coherence function approach, which is defined between the motor current and vibration signals, for induction motors. Hence, the high performance of Elman's RNN was shown by means of two different applications.     

Constituents,Oxidant-Antioxidant Profile,and Antimicrobial Capacity of the Essential Oil Obtained from Ferulago Sandrasica Peşmen and Quézel

Chemical constituents, total phenolic content, total oxidant status, total antioxidant status, lipid hydroperoxides, total free –SH levels, and antimicrobial activity of essential oil obtained from the Ferulago sandrasica (Umbelliferae) were investigated. The essential oil was obtained by hydrodistillation using a Clevenger-type apparatus. The chemical constituents were analyzed by gas chromatography‐mass spectrometry. The main components of the essential oil were ocimene (30.5%), carene-δ-3 (27.4%), and α-pinene (17.8). The antimicrobial activity was tested by a disc diffusion method against E. coli MC 400, E. coli ATCC 25922, E. coli 0157 H7, E. colaecea ATCC 23355, E. feacalis ATCC 19433, P. aeruginosa NRRL B-2679, S. aureus ATCC 25923, B. nischenoformis NRRL B-1001, S. aureus ATCC 33862, B. cereus NRRL B-3711, B. subtilis NRRL B-209, M. luteus NRRL B-1013, L. monocytogenes ATCC 7644, B. subtulis ATCC 6633.     

Evaluation of the effects of different remineralizing agents on Streptococcus mutans biofilm adhesion

The aim of the study was to compare the effects of different remineralization methods that are well established in clinical and daily use on S. mutans biofilm adhesion. In this study 72 human third molars were used. From each tooth two pieces of 4?mm x 7?mm enamel blocks were acquired. The samples were divided into 6 groups in which include 10 samples per time period (24h and 48?h) and for each remineralization method; control, flouride, ozone, CPP-ACP, arginine, novamin. After remineralization procedures, enamel surfaces were covered with saliva. 10⁵ CFU/mL of active S. mutans culture were inoculated onto the samples. S. mutans colonies were counted with Plate Count Agar (PCA) decimal dilution method. Micromorphologic effects of different remineralization methods were observed by Scanning Electron Microscopy (SEM). The most S. mutans biofilm formation for both time periods was observed in the control group whereas the less biofilm adhesion was showed in the arginine group. There were no statistically significant differences among remineralization agents (p?>?0.05). In the control group there was statistical difference between 24?h and 48?h (p?<?0.005) but in the other study groups there were no significant difference between the time periods (p?>?0.05). Remineralization agents did not significant differ on S. mutans biofilm adhesion.     

Ni(II) removal from aqueous solutions using cone biomass of Thuja orientalis

The biomass of terrestrial-plant materials has high removal capacities for a number of heavy metal ions. The Ni(II) biosorption capacity of the cone biomass of Thuja orientalis was studied in the batch mode. The biosorption equilibrium level was determined as a function of contact time, pH, temperature, agitation speed at several initial metal ion and adsorbent concentrations. The removal of Ni(II) from aqueous solutions increased with adsorbent concentration, temperature and agitation speed of the solution were increased. The biosorption process was very fast; 90% of biosorption occurred within 3 min and equilibrium was reached at around 7 min. It is found that the biosorption of Ni(II) on the cone biomass was correlated well (R2 > 0.99) with the Langmuir equation as compared to Freundlich, BET Temkin and D-R isotherm equation under the concentration range studied. According to Langmuir isotherm, the monolayer saturation capacity (Q(o)) is 12.42 mg g(-1). The pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models were applied to test the experimental data for initial Ni(II) and cone biomass concentrations. The pseudo-second-order kinetic model provided the best correlation of the used experimental data compared to the pseudo-first-order and intraparticle diffusion kinetic models. The activation energy of biosorption (E(a)) was determined as 36.85 kJ mol(-1) using the Arrhenius equation. This study indicated that the cone biomass of T. orientalis can be used as an effective and environmentally friendly adsorbent for the treatment of Ni(II) containing aqueous solutions.