Sorption of Differently Charged Gold Nanoparticles on Synthetic Pyrite

Sorption of nanoparticles on mineral surfaces has been well recognized for its environmental implication. For certain gold ore deposits, sorption of gold nanoparticles (AuNPs) on pyrite may constitute a critical step in the metallogenesis process, yet it has not been adequately investigated. In this work, we synthesized negatively charged, positively charged AuNPs and pyrite respectively, and experimentally studied sorption of AuNPs on pyrite in an anaerobic environment. The effects of AuNPs charge characteristics, pH, hexadecyl trimethyl ammonium bromide (CTAB) concentration, and ionic strength were evaluated. For the negatively charged AuNPs, almost no sorption was observed owing to the electrostatic repulsion between the AuNPs and pyrite surface (with a measured isoelectric point of 2.0). In contrast, positively charged AuNPs could be significantly adsorbed on pyrite through electrostatic attraction, with the sorption extent decreasing with the increase of pH (2.2–9.1). However, the adsorption of CTAB from the solution was found to increase with the increase of pH. Furthermore, deliberately added CTAB seemed to inhibit the sorption of AuNPs. Our study not only demonstrates that the electrostatic interaction is the dominant mechanism in the sorption of AuNPs on pristine pyrite, but also reveals the important competitive relation between AuNPs and CTAB in the sorption process

Body mass index is associated with physical performance in suburb-dwelling older chinese: a cross-sectional study.

Physical performance is reported to have various beneficial effects on human health, especially in older individuals. Although such effects are associated with body mass index (BMI), the relationship between BMI and physical performance has not been clarified.We conducted a cross-sectional study of 966 suburb-dwelling Tianjin individuals aged ≥ 60 years (average age 67.5±6.02, men 435, women 531). Mobility, balance, and muscle strength were assessed by walking speed, timed up-and-go test (TUGT), and grip strength, respectively. The subjects were categorized into three groups based on BMI (kg/m2) as follows: normal weight, 18.5 ≤ BMI ≤ 23.9; overweight, 24.0 ≤ BMI ≤ 27.9; and obese, BMI ≥ 28.0.After adjusting for all other variables, relative grip strength decreased when BMI increased in both men and women (P for trend <0.001 and <0.001, respectively). BMI may be negatively associated with TUGT performance in the women only. There was no apparent association between walking speed and BMI in either sex, but after adjusting for age, walking speed was faster when BMI increased in women (P for trend= 0.0162).This study suggests that in older individuals, higher BMI is associated with poor muscle strength in both sexes

Subject characteristics according to categories of BMI.

<p>1 BMI, body mass index; IPAQ, International Physical Activity Questionnaire; TC, total cholesterol; TG, total triglycerides; GLU, fasting blood glucose.</p><p>2 Obtained by using ANOVA for continuous variables and chi-square for variables of proportion.</p><p>3 Mean; 95% CI in parentheses (all such values).</p><p>4 * p < 0.05 versus Normal weight; † p < 0.05 versus Over weight.</p><p>Subject characteristics according to categories of BMI.</p

Adjusted the relationship between BMI and physical performance.

<p>¹ Obtained by using ANCOVA;</p><p>² Adjusted for age;</p><p>³ Additionally adjusted for educational level, profession; diabetes, hypertension, hyperuricemia, stroke, coronary heart disease, arthritis and cancer, history of smoking and drinking habits; International Physical Activity Questionnaire (IPAQ).</p><p>⁴ Mean; 95% CI in parentheses (all such values).</p><p>⁵ *p < 0.05 versus Normal weight;</p><p>†p < 0.05 versus Over weight.</p><p>Adjusted the relationship between BMI and physical performance.</p