Compressive behavior of stirrup-confined concrete columns: size effect and a size-dependent stress-strain model

Numerous studies have indicated the existence of size effect on axial compression behavior of stirrup-confined concrete columns. However, most of these studies have been stressed in terms of nominal compressive strength. The investigation on the size effect of axial strain (at peak load) and descending branch was limited. In this study, the size effect behavior of square stirrup-confined concrete columns under axial compression was explored, by using 3-D mesoscale simulation method. Based on the numerical and available experimental results, the influence of specimen size on the peak axial stress (i.e., the compressive strength), the corresponding strain and the softening rate were explored. Moreover, the quantitative relationships between specimen size and the peak axial stress, the corresponding strain and the softening rate for circular and square stirrup-confined concrete columns were derived. Finally, considering the size effect of peak axial stress, the corresponding strain and the softening rate, a novel stress-strain model describing the axial compression behavior of stirrup-confined concrete was developed. The proposed model was verified by comparing with the available experimental results and the existing models provided.

Enzyme systems involved in glucosinolate metabolism in Companilactobacillus farciminis KB1089

Cruciferous vegetables are rich sources of glucosinolates (GSLs). GSLs are degraded into isothiocyanates, which are potent anticarcinogens, by human gut bacteria. However, the mechanisms and enzymes involved in gut bacteria-mediated GSL metabolism are currently unclear. This study aimed to elucidate the enzymes involved in GSL metabolism in lactic acid bacteria, a type of gut bacteria. Companilactobacillus farciminis KB1089 was selected as a lactic acid bacteria strain model that metabolizes sinigrin, which is a GSL, into allylisothiocyanate. The sinigrin-metabolizing activity of this strain is induced under glucose-absent and sinigrin-present conditions. A quantitative comparative proteomic analysis was conducted and a total of 20 proteins that were specifically expressed in the induced cells were identified. Three candidate proteins, β-glucoside-specific IIB, IIC, IIA phosphotransferase system (PTS) components (CfPttS), 6-phospho-β-glucosidase (CfPbgS) and a hypothetical protein (CfNukS), were suspected to be involved in sinigrin-metabolism and were thus investigated further. We hypothesize a pathway for sinigrin degradation, wherein sinigrin is taken up and phosphorylated by CfPttS, and subsequently, the phosphorylated entity is degraded by CfPbgS. As expression of both pttS and pbgS genes clearly gave Escherichia coli host strain sinigrin converting activity, these genes were suggested to be responsible for sinigrin degradation. Furthermore, heterologous expression analysis using Lactococcus lactis suggested that CfPttS was important for sinigrin degradation and CfPbgS degraded phosphorylated sinigrin.

Relationships between job stress, psychological adaptation, negative affective states and Internet gaming disorder among migrant factory workers in China: cross-sectional survey (Preprint)

BACKGROUND Factory workers make up a large proportion of China’s internal migrants and may be highly susceptible to Internet gaming disorder (IGD). However, little research on IGD has been conducted in this population. OBJECTIVE This study aims to investigate the prevalence and potential factors of IGD among migrant factory workers in China. Furthermore, it aims to examine a mediation model based on the framework of the general strain model among migrant factory workers. METHODS A stratified multi-stage sampling approach was used for recruitment. In the first stage, the research team randomly selected 16 factories in Longhua district, and then randomly selected three to four workshops from each factory. All full-time employees aged ≥18 years in the selected workshops were invited to participate in the study. A total of 2,023 factory workers completed a self-administered questionnaire between October and December 2019. Structural equation modeling was conducted to test the proposed mediation model. RESULTS Most of the participants (67.3%) were male, aged 35 years old or below (71.7%), and without teritary education (91%). The prevalence of probable depression, probable anxiety, and IGD was 39.3%, 28.7%, and 7.5%. Being male, younger age, and shorter duration of living in Shenzhen were associated with higher IGD scores. Job stress was significantly associated with IGD (B=.02, β=.11, p=.01) but not with negative affective states (B=.04, β=.01, p=.77). Psychological adaptation was significantly associated with negative affective states (B=-2.93, β=-.37, p<.001) but not with IGD (B=.04, β=.09, p>.05). Negative affective states were positively associated with IGD (B=.02, β=.27, p<.001). The indirect effect of psychological adaptation (B=-.05, β=-.10, 95%CI=-.14 to -.07, p=.004) but not job stress (B=.001, β=.003, 95%CI=-.02 to .03, p=.76) on IGD through negative affective states was statistically significant. The significant indirect effect and insignificant direct effect of psychological adaptation on IGD suggested a full mediation effect of negative affective states. CONCLUSIONS This study provides evidence for applying the general strain model to understand IGD among migrant factory workers. Efforts to prevent negative affective states, IGD and other risk behaviors in this special and huge population in China are in urgent need. The observed psychological factors and mechanisms are modifiable, and can inform the design of evidence-based prevention programs for IGD in this population.