Comparing interventions to reduce boredom in a low mental workload environment.

Boredom is a common workplace problem. Previous research has suggested that repetitive and monotonous work tasks may lead to boredom. However, these tasks have been reduced due to increased workplace automation. Thus, the current cause of boredom may be due to low mental workload. This research developed a general boredom model and compared the effects of feedback type (performance and ranking) and intervention method (game and quiz) on boredom and task performance. Results revealed that the secondary task interventions can reduce boredom and feedback could shorten the response time. Gender also had a significant influence on response time. Notably, results revealed a 4% probability of task failure during the experiment, indicating other interventions are also required. This research indicates that interventions to reduce boredom caused by low mental workload should be designed differently from tasks that have been designed to combat the boredom caused by repetitive and monotonous work.

Regional differences in the effect of interpersonal relationship on trust and trustworthiness in China.

Guanxi, which literally means interpersonal relationship or social connections, plays an important role in achieving business success in China. This study investigates the effect of interpersonal relationship on trust and trustworthiness in four regions in China. Eighty pairs of close friends participated in the experiment: 20 pairs from Beijing, 20 pairs from Guangdong, 20 pairs from Shanghai, and 20 pairs from Chongqing. A cooperation experiment based on a two-tier simulated supply chain was conducted, in which the participant who played as a supplier solicited demand forecast information from the participant who played as a retailer to plan production. Participants were instructed to perform two tasks: one with a "friend" counterpart and one with a "stranger" counterpart. The results demonstrated regional differences in the effects of interpersonal relationship on trust and trustworthiness: the effect of interpersonal relationship was greater in Guangdong than in the other regions. Additionally, a quantified classification of trustworthiness-trust was proposed by clustering analysis. The type of self-protective trustworthiness and altruistic trust occupied an overwhelming majority in each region, followed by the type of altruistic trustworthiness and self-protective trust, the type of altruistic trustworthiness and altruistic trust, and the type of self-protective trustworthiness and self-protective trust. Regional differences in the distribution proportions in the four types were discovered.

A hollow-fiber membrane extraction process for recovery and separation of lactic acid from aqueous solution.

An energy-efficient hollow-fiber membrane extraction process was successfully developed to separate and recover lactic acid produced in fermentation. Although many fermentation processes have been developed for lactic acid production, an economical method for lactic acid recovery from the fermentation broth is still needed. Continuous extraction of lactic acid from a simulated aqueous stream was achieved by using Alamine 336 in 2-octanol contained in a hollow-fiber membrane extractor. In this process, the extractant was simultaneously regenerated by stripping with NaOH in a second membrane extractor, and the final product is a concentrated lactate salt solution. The extraction rate increased linearly with an increase in the Alamine 336 content in the solvent (from 5 to 40%). Increasing the concentration of the undissociated lactic acid in the feed solution by either increasing the lactate concentration (from 5 to 40 g/L) or decreasing the solution pH (from 5.0 to 4.0) also increased the extraction rate. Based on these observations, a reactive extraction model with a first-order reaction mechanism for both lactic acid and amine concentrations was proposed. The extraction rate also increased with an increase in the feed flow rate, but not the flow rates of solvent and the stripping solution, suggesting that the process was not limited by diffusion in the liquid films or membrane pores. A mathematical model considering both diffusion and chemical reaction in the extractor and back extractor was developed to simulate the process. The model fits the experimental data well and can be used in scale up design of the process.

Enhanced amylase production by Bacillus subtilis using a dual exponential feeding strategy.

A recombinant Bacillus subtilis strain (ATCC 31784) haboring the plasmid pC194 with a thermostable alpha-amylase gene was cultured in a 22-l B. Braun Biostat C fermenter. Traditional batch operations suffer from low cell mass and protein productions because a high initial glucose concentration causes substrate inhibition and also product inhibition due to acetate accumulation. An exponential fed-batch strategy to prevent these inhibitions was developed in this work. The host strain is auxotrophic for phenylalanine, tyrosine and tryptophan. Due to low solubilities of tyrosine and tryptophan in the feed stream, tyrosine and tryptophan were dissolved separately in ammonia water to form a second feed stream. By dual feeding both streams at different exponential feed rates, a high cell density of 17.6 g/l and a final alpha-amylase activity of 41.4 U/ml and the overall biomass yield of 0.39 g cell/g glucose were achieved.