How do Virtual Badges Incentivize Voluntary Contributions to Online Communities?

Online communities rely heavily on badges to incentivize users to participate in voluntary activities. We examine the relationship between earned badges/pursued badges and contributions in the Stack Overflow question and answer community. Our main results reveal that different levels of earned and pursued badges increase the amount of subsequent answering activity. In addition, earned gold badges are the most influential in the motivation of users while earned bronze badges are the least impactful. Furthermore, the effect of badges involves positive spillovers from higher levels of earned badges to lower ones. Our findings offer important theoretical and managerial implications for online communities.     

Experimental Simulation on Chemical-looping Combustion of Cold Model

The pressure profiles, gas velocities, solid circulation rate, solids flux, residence time distribution of gas and particles in chemical-looping combustion reactors and gas leakage were studied in a cold flow model unit. And these parameters in both air and fuel reactors were measured in the experimental stage. The experimental results show that gas fluidization velocity in the air reactor is 1.8 m/s, gas fluidization velocity in the fuel reactor 0.5 m/s, and the bed materials inventory of the two reactors between 1.2 to 3.15 kg. The first cold flow model results show that the solid circulation rates are sufficient. The appropriate operating conditions are optimized and the summary of final changes is made the on cold model. The proposed design solutions are currently being verified in a cold flow model simulating the actual reactor (hot) system. This paper presents an overview of the research performed on a cold flow model and highlights the current status of the technology.     

Impact of frying on key fatty acid ratios of canola oil

The study was carried out to investigate the changes in saturated (SFA), monoene (MUFA), trans (TFA), and polyunsaturated (PUFA) fatty acids and the key fatty acid ratios (SFA/UFA, cis PUFA/SFA, C18:2/C16:0 and C18:3/C16:0) during potato chips frying in canola oil using single bounce attenuated total reflectance FTIR (SB‐ATR‐FTIR) spectroscopy. The data obtained from GC‐FID were used as reference. The calibration of main fat groups and their key fatty acid ratios were developed by partial least square (PLS) regression coefficients using 4000 to 650 cm^?1 spectral range. FTIR PLS regression for the predicted SFA, MUFA, TFA, and PUFA were found 0.999, 0.998, 0.998, and 0.999, respectively, whereas for SFA/UFA, cis PUFA/SFA, C18:2/C16:0 and C18:3/C16:0 the regression coefficients were 0.991, 0.997, 0.996, and 0.994, respectively. We conclude that FTIR‐PLS could be used for rapid and accurate assessment of changes in the main fat groups and their key fatty acid ratios ratio during the frying process. Practical applications: FTIR‐ATR method is very simple, rapid, and environmentally friendly. No sample preparation is required and one drop of oil is enough for FTIR analysis. The proposed method could be applied for quick determination of key fatty acid ratios in the food processing industry.     

The survival of E. coli O157:H7, S. Typhimurium and L. monocytogenes in black carrot (Daucus carota) juice

In this study the survival and growth patterns of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in various concentrations of black carrot juice were investigated during incubation period at 4 °C and 37 °C for 7 days. Several parameters, such as juice concentration (%), pH, incubation temperature (°C) and time (days) were found effective on the survival of pathogens tested. Although L. monocytogenes has been found to be the less resistant microorganism to the variable conditions, there were only ca. 1 and 2 log reductions in the number of the cells in the juice samples incubated at 4 °C for 2 and 7 days, respectively. Incubating at low temperature (4 °C) enhanced the survival of test microorganisms.     

Phase Identification of La-Doped Hard Magnetic Barium Ferrite Using Artificial Neural Network

A model based on an artificial neural network (ANN) was designed for the simulation and estimation of 2 theta and intensity values obtained by X-Ray Diffraction (XRD) of pure and La-doped barium ferrite powders which have been synthesized in ammonium nitrate melt. Its performance is evaluated by the influences of different La content, sintering temperature, Fe/Ba ratio, and washed in HCl (or not washed in HCl) samples. The XRD patterns of samples estimated by the ANN agree well with the experimental values, indicating that the model is reliable and adequate.     

Evolution of fermenting microbiota in tarhana produced under controlled technological conditions

The purpose of this study was to evaluate the evolution of lactic acid bacteria (LAB) and yeasts during the fermentation of tarhana produced with some pasteurised ingredients and carried out at 30 and 40 °C. The chemical parameters were those typical for tarhana production. Coliform bacteria were not detected during fermentation, while LAB and yeasts were in the range 10⁷-10⁸ colony forming units (CFU) g⁻¹. Plate counts showed an optimal development of both fermenting microbial groups and the differences in cell concentrations were not significant (P > 0.05). LAB were isolated during fermentation and grouped on the basis of phenotypic and polymorphic characteristics. LAB isolates were identified by a combined genetic approach consisting of 16S/23S rRNA intergenic spacer region (ITS) and partial 16S rRNA gene sequencing as Pediococcus acidilactici, Lactobacillus plantarum and Lactobacillus brevis. Hence, the pasteurisation of the vegetable ingredients, excluded wheat flour, enhanced the hygienic conditions of tarhana without influencing the normal evolution of LAB. However, the fermentation at 40 °C favoured pediococci, while the production at 30 °C was mainly characterised by lactobacilli. Yeasts, identified by the restriction fragment length polymorphism (RFLP) of the 5.8S ITS rRNA gene, were mainly represented by the species Saccharomyces cerevisiae in both productions.     

Frequency of Escherichia coli O157:H7 in Turkish cattle

In this study, five abattoirs in Istanbul were visited between January 2000 and April 2001. During these visits, 330 cattle were selected by a systematic sampling method. Cattle were examined clinically and breed, age, and sex were recorded. Rectal swabs were taken immediately after slaughter. Immunomagnetic separation was performed, and sorbitol-negative colonies were selected on sorbitol MacConkey agar with cefixime and tellurite (CT-SMAC agar). These colonies were checked for 4-methylenebelliferyl-beta-D-glucuronide, indol, rhamnose, and urease activity and motility. Serotypes of bacteria were determined by using antisera specific for Escherichia coli O157 and H7. All cattle selected were clinically healthy. Of 88 sorbitol-negative colonies selected on CT-SMAC agar, isolates from only 14 (4.2%) cattle reacted with anti-O157, and 13 of these isolates also reacted with anti-H7. E. coli O157:H7 was isolated from all breeds, but the numbers of isolates were largest for Holstein and Swiss Brown cows. E. coli O157:H7 was most frequently isolated from 2-year-old cattle. Similarly, it was most frequently isolated from male cattle. E. coli O157:H7 was isolated from cattle slaughtered in four of the five abattoirs studied.     

A Novel Approach for Determination of Free Fatty Acids in Vegetable Oils by a Flow Injection System with Manual Injection

A non-aqueous flow injection method for determining free fatty acid (FFA) content in corn and sunflower oil samples was developed. A single-line manifold system was built by modification of an HPLC for flow injection analysis (FIA). Without pre-treatment, oil samples were injected into a n-propanol solution containing KOH and phenolphthalein (PHP). The main parameters, such as flow rate of carrier phase, length, geometry, inner diameters of the coils and reagent concentration were all optimized. The proposed FIA method was validated for precision, accuracy, linear region, limit of detection (LOD) and limit of quantification (LOQ). The intra- and inter-day measurements of the precision of the method were found to be within the limits of acceptance criteria (RSD < 1%), and were rugged when the method was performed by a different analyst. The linear concentration range was calculated as 0.09–1.50 and 0.07–1.40 FFA% for corn and sunflower oils, correspondingly. The LOD and LOQ were found to be 7.53 × 10⁻⁴–2.28 × 10⁻³ oleic acid % and 7.11 × 10⁻⁴–2.23 × 10⁻³ oleic acid % for corn and sunflower oils, respectively. The results were compared with those obtained by the AOCS (Ca-5a-40) method using statistical t and F tests, and a significant difference was not observed between the methods at a 95% confidence level. The proposed method is suitable for quality control of routine applications due to its simplicity, high sample throughput, and economy of solvents and sample, offering considerable promise as a low cost analytical system that needs minimum human intervention over long periods of time.     

Mechanical and thermal properties of a novel composite prepared with epoxy resin and lateritic ore

Composites made from epoxy resins (ERs) are one of the important polymer groups used in different industries due to their good mechanical and thermal properties. Many attempts have been done to improve both the mechanical and the thermal properties of ER composites and to lower the cost of ER composites with addition of inexpensive fillers such as calcium carbonate, kaolin clays, silica, talc, etc. In this study novel lateritic ore (LO) filler was used in diglycidyl ether of bisphenol A‐type ER. Different addition percentages (5–20%) of both natural LO (nLO) and modified LO (mLO) into ER were tested to determine the influence on mechanical and thermal properties of newly produced composites. Surface hardness, Young's modulus, tensile strength, elongation at break, water sorption, adhesion, and thermal stability of composites were determined and were compared with pure ER. Results showed that the addition of nLO/mLO has positive effect on mechanical and thermal properties. Morphological characterization by scanning electron microscopy and structural characterization by X‐ray diffraction revealed that addition nLO/mLO distributed homogenously throughout the composites. POLYM. COMPOS. 34:1375–1381, 2013. © 2013 Society of Plastics Engineers