Co‐optimization of SnS absorber and Zn(O,S) buffer materials for improved solar cells

Thin‐film solar cells consisting of earth‐abundant and non‐toxic materials were made from pulsed chemical vapor deposition (pulsed‐CVD) of SnS as the p‐type absorber layer and atomic layer deposition (ALD) of Zn(O,S) as the n‐type buffer layer. The effects of deposition temperature and annealing conditions of the SnS absorber layer were studied for solar cells with a structure of Mo/SnS/Zn(O,S)/ZnO/ITO. Solar cells were further optimized by varying the stoichiometry of Zn(O,S) and the annealing conditions of SnS. Post‐deposition annealing in pure hydrogen sulfide improved crystallinity and increased the carrier mobility by one order of magnitude, and a power conversion efficiency up to 2.9% was achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparison of fuzzy inference system (FIS), FIS with artificial neural networks (FIS + ANN) and FIS with adaptive neuro-fuzzy inference system (FIS + ANFIS) for inventory control

Conventional inventory models mostly cope with a known demand and adequate supply, but are not realistic for many industries. In this research, the fuzzy inference system (FIS) model, FIS with artificial neural network (ANN) model and FIS with adaptive neuro-fuzzy inference system (ANFIS) model in which both supply and demand are uncertain were applied for the inventory system. For FIS model, the generated fuzzy rules were applied to draw out the fuzzy order quantity continuously. The order quantity was adjusted according to the FIS model with the evaluation algorithm for the inventory model. The output of FIS model was also used as data for FIS + ANN and FIS + ANFIS models. The FIS + ANFIS model was studied with three membership functions; trapezoidal and triangular (Trap), Gaussian and bell shape. Inventory costs of the proposed models were compared with the stochastic economic order quantity (EOQ) models based on previous data of a case study factory. The results showed that the FIS + ANFIS_Gauss model gave the best performance of total inventory cost saving by more than 75 % compared to stochastic EOQ model.     

Hydrodynamics and mass transfer behavior in multiple draft tube airlift contactors

The draft tube configuration significantly affected the performance of an airlift contactor. The multiple draft tube configuration was demonstrated to give a better gas-liquid mass transfer when compared with a conventional one-draft-tube system. The airlift with a larger number of draft tubes allowed a higher level of bubble entrainment, which rendered a high downcomer gas holdup. This resulted in a higher overall gas holdup in the contactor. Liquid velocity was also enhanced by increasing the number of draft tubes. The ratio between downcomer and riser cross sectional areas, A _d /A _r , had a great effect on the system performance, where a larger A _d /A _r led to a lower downcomer liquid velocity and smaller quantity of gas bubbles being dragged into the downcomer. This resulted in low gas holdup, and consequently, low gas-liquid interfacial mass transfer area, which led to a reduction in the overall volumetric mass transfer coefficient. The presence of salinity in the system drastically reduced the bubble size and subsequently led to an enhancement of gas entrainment within the system. As a result, higher gas holdups and gas-liquid interfacial area were observed, and hence, a higher rate of gas-liquid mass transfer was obtained.     

Synthesis,structural characterization,and magnetic property of nanostructured ferrite spinel oxides (AFe2O4, A = Co,Ni and Zn)

Nanostructured ferrite spinels AFe₂O₄ (A = Co, Ni, Zn) were successfully synthesized via a co-precipitation method using oxalate salt as a precursor in an anionic surfactant system in combination with a simple calcination process. High crystallinity samples of nanoparticle spinels in a grain size range of 15–100 nm were obtained by varying the calcination temperature (300–700 °C) and time (1–5 h). Their pore sizes were controlled in a range of 3 nm up to a hundred nm by tailoring the calcination conditions. Raising the calcination temperature was found to decrease the Brunauer–Emmett–Teller (BET) surface area, and broaden the pore structure due to enhanced crystal growth and agglomeration of interparticles of spinels. Transmission electron microscopy (TEM) images of ferrite spinels calcined at 300 °C showed mesoporous structures with narrow pore size distribution, and the maximum BET surface area of CoFe₂O₄, NiFe₂O₄ and ZnFe₂O₄ were found at 201 (Co), 315 (Ni), and 273 (Zn) m² g⁻¹, respectively. The magnetic hysteresis loops of the ferrite spinels at room temperature demonstrated ferromagnetism in CoFe₂O₄, superparamagnetism–ferromagnetism in NiFe₂O₄, and paramagnetism in ZnFe₂O₄. The highest saturation magnetization (M_s), remanent magnetization (M_r), and coercivity (H_c) were obtained from high crystallinity spinels calcined at 700 °C. Nanostructured AFe₂O₄ with high surface area and mesoporosity promises potentials as novel magnetic catalysts.     

Structure of the olfactory receptor organs,their GABAergic neural pathways,and modulation of mating behavior,in the giant freshwater prawn,Macrobrachium rosenbergii

In the giant male prawn, Macrobrachium rosenbergii, the olfactory system is thought to be the main pathway for modulating sexual behavior through pheromone perception. In this report, we first used gross anatomical, histological, and SEM methods to describe the structures of the olfactory receptors (sensilla setae), their neural pathways, and possible role in modulating mating behavior. On the surfaces of antennule and antenna filaments there are four types of sensory receptors, viz single spike‐like setae, single flagellum‐like setae, multiple flagella‐like setae, and aesthetascs (ASs). The ASs, which had previously been proposed to be odor receptor setae, are found only on the short filament of lateral antennule (slAn). Each AS on the slAn connects with olfactory receptor neurons (ORNs), whose axons form an outer central antennule nerve (ocAnNv), which then connects with the olfactory neutrophil (ON) of the brain. Thus, the slAn is the major olfactory organ that conveys sensory inputs from each AS to the ON within the deutocerebrum. GABA immunoreactivity was present in ASs, neurons of ORNs, inner central antennular, lateral tegumentary nerve, ocAnNv and the ON, inferring that GABA is the likely neurotransmitter in modulating olfaction. Disruption of the slAn by ablation or covering with Vaseline, resulted in significant reduction of mating behavior, indicating that this organ is crucial for sex pheromone perception. Identification of the active pheromones and further bioassays are now being performed. Microsc. Res. Tech. 76:572–587, 2013. © 2013 Wiley Periodicals, Inc.     

Selective Extraction of Lutein from Alcohol Treated Chlorella vulgaris by Supercritical CO2

A pretreatment process using alcohol for the removal of chlorophyll a, b and β‐carotene from Chlorella vulgaris was developed to improve the yield and selectivity of lutein in the extract obtained by supercritical carbon dioxide extraction. Supercritical carbon dioxide extraction was carried out after pretreatment in the pressure range of 20 to 40 MPa and the temperature range of 40 to 80 °C. Ethanol and methanol were selected as elution solvents, of which ethanol was found most suitable for the elution, or pretreatment, process. The amounts of lutein and other compounds were analyzed by HPLC with the mixture of methanol and THF as the mobile phase. The amount of lutein in the extract increased with pressure, but decreased with extraction temperature. The highest recovery percentage and the selectivity of lutein were around 52.9 ± 0.02 % and 43.1 ± 0.02 %, respectively, obtained from supercritical carbon dioxide extraction with pretreatment and ethanol entrainer at 40 MPa and 40 °C.     

Nitrogen compounds removal in a packed bed external loop airlift bioreactor

A packed bed external loop airlift bioreactor (PBELAB) was proposed as an alternative treatment system for wastewater containing ammonia and nitrate compounds. The 60L PBELAB consisted of aeration and non-aeration zones, both of which were packed with plastic bioballs to enhance the surface area for the attachment of bacteria. The system was able to achieve complete removal of all nitrogen compounds with simultaneous nitrification and denitrification, i.e., ammonia was decomposed in the aeration zone and nitrate was biodegraded in the non-aeration zone. At normal operation, the nitrification rate obtained from the system was in the range of 0.14-0.87 gNH₃-N/m²d and the denitrification rate was 0.04 gNO₃-N/m²d. The factors found to have great influence on the system included dissolved oxygen concentration and biofilm thickness. In addition, PBELAB was proven to perform well under nitrate shock load condition.     

Electrospun poly(L‐lactic acid)/hydroxyapatite composite fibrous scaffolds for bone tissue engineering

Poly(L ‐lactic acid) (PLLA) is one of the most studied synthetic biodegradable polymeric materials as a bone graft substitute. Taking into account the osteoconductive property of hydroxyapatite (HAp), we prepared fibrous matrices of PLLA without and with HAp particles in amounts of 0.25 or 0.50% (w/v, based on the volume of the base 15% w/v PLLA solution in 70:30 v/v dichloromethane/tetrahydrofuran). These fibrous matrices were assessed for their potential as substrates for bone cell culture. The presence of HAp in the composite fibre mats was confirmed using energy dispersive X‐ray spectroscopy mapping. The average diameters of both neat PLLA and PLLA/HAp fibres, as determined using scanning electron microscopy, ranged between 2.3 and 3.5 µm, with the average spacing between adjacent fibres ranging between 5.7 and 8.5 µm. The porosity of these fibrous membranes was high (ca 97–98%). A direct cytotoxicity evaluation with L929 mouse fibroblasts indicated that the neat PLLA fibre mats released no substance at a level that was toxic to the cells. The presence of HAp particles at 0.50% w/v in the PLLA fibrous scaffolds not only promoted the attachment and the proliferation of MC3T3‐E1 mouse pre‐osteoblastic cells, but also increased the expression of osteocalcin mRNA and the extent of mineralization after the cells had been cultured on the scaffolds for 14 and 21 days, respectively. The results obtained suggested that the PLLA/HAp fibre mats could be materials of choice for bone tissue engineering. Copyright © 2009 Society of Chemical Industry