Could 70 Be the New 60? Investigating the Association Between Internet Use and Subjective Age Among Chinese Older Adults.

OBJECTIVES: The widespread use of the Internet brings both opportunities and challenges for older adults. To understand its potential benefits and drawbacks, we focus on the association between Internet use and multiple indicators of subjective age (threshold age, felt age, and look age) and the underlying mechanisms. METHODS: A nationally representative sample of older adults aged 60 and over from 3 waves (collected in 2016, 2018, and 2020) of the China Longitudinal Aging Social Survey was used in the analysis. A 3-step random-effect model and mediation analysis were used to examine the relationship between Internet use and subjective age and the mediating roles of volunteering and feeling valued by society. Structural equation modeling with a serial multiple mediation model was conducted for robustness checks. RESULTS: The participants generally considered 70 as the threshold for "old age." Although the mediation analysis did not show a significant indirect effect of Internet use on older adults' subjective age through volunteering, Internet use was linked with older adults' subjective age directly and indirectly through feeling valued by society. Compared to moderate Internet users, nonusers felt less valued by society and, therefore, had a younger threshold age and older subjective ages. Heavy Internet users showed a lower level of participation in volunteer activities. DISCUSSION: The results support previous theories about the mental and social health benefits of Internet use among older adults. However, Internet use intensity should receive more attention; excessive use may reduce the duration of older adults' offline social interactions.

Removal of cadmium by bioflocculant produced by Stenotrophomonas maltophilia using phenol-containing wastewater.

Bioflocculants have been applied in numerous applications including heavy metals removal. A major bottleneck for commercial application of bioflocculant is its high production cost. Phenol-containing wastewater are abundantly available. However, the toxic phenol inhibited the microbial activities in the subsequent fermentation processes. Consequently, strains that can secrete phenol-degrading enzymes and simultaneously produce bioflocculants through directly degrading the phenol are of academic and practical interests. A phenol-degrading strain, Stenotrophomonas maltophilia ZZC-06, which can produce the bioflocculant MBF-06 using phenol-containing wastewater, was isolated in this study. The effects of culture conditions including initial pH, dissolved oxygen, phenol concentration, inoculum size, and temperature on MBF-06 production were analyzed. The experimental results showed that over 90% flocculating activity was achieved when the phenol was used as a carbon source and 4.99 g/L of MBF-06 was achieved under the optimized condition: 2.0% dissolved oxygen, 800 mg/L phenol concentration, 10% inoculum size, an initial pH of 6.0, and a temperature of 30 °C. The bioflocculant MBF-06 contained 71.2% polysaccharides and 27.9% proteins. The feasibility of cadmium removal using MBF-06 was evaluated. The highest flocculating efficiency for cadmium was 81.43%. This study shows for the first time that Stenotrophomonas maltophilia ZZC-06 can directly convert phenol into a bioflocculant, which can be used to effectively remove cadmium.

Production of bioflocculants prepared from formaldehyde wastewater for the potential removal of arsenic.

A novel bioflocculant (MBF-79) prepared using formaldehyde wastewater as carbon resource was investigated in the study. The optimal conditions for bioflocculant production were determined to be an inoculum size of 7.0%, initial pH of 6.0, and formaldehyde concentration of 350 mg/L. An MBF-79 of 8.97 g/L was achieved as the maximum yield. Three main elements, namely C, H, and O, were present in MBF-79 with relative weigh percentages of 39.17%, 6.74%, and 34.55%, respectively. The Gel permeation chromatography analysis indicated that the approximate molecular weight (MW) of MBF-79 was 230 kDa. MBF-79 primarily comprised polysaccharide (71.2%) and protein (27.9%). Additionally, conditions for the removal of arsenic by MBF-79 were found to be MBF-79 at 120 mg/L, an initial pH 7.0, and a contact time 60 min. Under the optimal conditions, the removal efficiencies of arsenate (0.5 mg/L) and arsenite (0.5 mg/L) were 98.9% and 84.6%, respectively. Overall, these findings indicate bioflocculation offers an effective alternative method of decreasing arsenic during water treatment.