Biomedical subjects
Publications and source records attributed to Yi-Fu Chen.
The relative prevalence of substance use among African-American high school students living in rural, urban, and suburban areas was examined. Students in rural areas reported equivalent or higher rates of substance use than did students in urban or suburban areas. Attention to substance use prevention among rural African-American students is warranted.
In this study, the efficacy of the Strong African American Families Program (SAAF) was tested. The trial, which included 332 families, indicated that families who participated in SAAF experienced increases over time in regulated, communicative parenting; increases in targeted parenting behaviors, according to youths' reports; and low rates of high-risk behavior initiation among youths. Changes in regulated, communicative parenting mediated the intervention's impact on youths' recognition of changes in parenting, which in turn was linked to changes in youths' high-risk behavior.
Wafer grinding extraction solution was passed through a supported liquid membrane (SLM) that contained PC88A (2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester) as a carrier, to separate gallium from arsenic by selective permeation. The SLM separation process was conducted under various conditions. The kind of membrane supporter, the pH of the feed, the feed concentration, and the HCl content in the strip governed the concentration of gallium and arsenic in the strip phase. The conditions determined as optimal in the laboratory test were used to perform the pilot test. Well separation between gallium and arsenic was performed in both laboratory and pilot tests. Hydrophobic membrane polytetrafluoroethylene (PTFE) with 0.2 microm pores was the best of three membrane supporters. The most efficient separation was obtained using an acidic feed (pH at 1.8) with 1000 ppm gallium. Over a 12-h period of stripping, the striped Ga concentration increased with the HCl concentration from 0.5 to 2.0 M and then leveled off. The recovery rate in the pilot test exceeded that on the laboratory scale because the membrane area was greater. The pilot test yielded a high recovery percentage of gallium (at 91%) and a low recovery of arsenic (merely 1.3 ppm) in the strip over 72 h.
This work studied the decolorization of dye C.I. Reactive Blue 19 (RB-19) solution in a new gas-inducing reactor under continuous process. The decolorization behavior, decolorization kinetic, ozone utilization rate (UO3), and Chemical Oxygen Demand (COD) are examined under various operation conditions, such as input ADMI color values (ADMIo), input liquid flow rates (QL), input ozone gas concentrations (CO3,i), input gas flow rates (Qg), and agitation speeds (N). Experimental results of decolorization behavior indicate that the American Dye Manufactures Institute (ADMI) removal percentage (RADMI) decreases with increasing ADMI color value input rate or decreasing ozone input rate. For the study of ozone utilization rate, UO3 increases with increasing ADMI color value input rate or decreasing ozone input rate. The 70% ADMI removal percentage can be regarded as the index of the competition of dye and its unknown intermediates for ozone. In addition, the increase of the agitation speed can improve the ADMI removal percentage as well as the ozone utilization rate. A pseudo-first order kinetic model is adopted to describe the decolorization behavior. At steady state, the overall decolorization rate constant, kADMIs.s., can be expressed as a function of liquid flow rate, input ADMI color value, input ozone gas concentration, gas flow rate, and agitation speed. This correlation can be used to predict the ADMI color value at steady state (ADMIs.s.) and the reactor size in the continuous process. The deltaO3/deltaCOD is dependent on the liquid composition. The higher the dye concentration in the liquid, the higher the deltaO3/deltaCOD. The COD removal percentage (RCOD) and the ozone utilization rate can be further improved by using the continuous operation with two reactors in series.
This work investigates the separation of gallium and arsenic from the wafer grinding extraction solution. The wafer grinding extraction solution was generated using hot and concentrated nitric acid. In this study, adsorption technology was employed to remove the toxic arsenic from the extraction solution. Ferric hydroxide was the adsorbent employed to adsorb arsenic. The effects of pH value, contact time, absorbent dosage, and chloride ion concentration on the efficiency of adsorption of gallium and arsenic were investigated. The optimal conditions for recovering gallium and removing arsenic were a raw pH of 0.2, a contact time of 6min and a ferric hydroxide concentration of 30.4g/L. Additionally, adding chloric ions reduces the residual percentage of gallium (ReGa) and the percentage of arsenic removed (RAs). Under these optimal conditions, ReGa and RAs are 100 and 80%, respectively.
To obtain a better treatment efficiency for dye or textile wastewater, a semi-batch and a continuous peroxone process using a new gas-inducing reactor were investigated in this study. In the semi-batch peroxone process, the results show that the peroxone process does not improve the color value (ADMI) removal rate, regardless of the pH value. However, the chemical oxygen demand (COD) removal rate could be enhanced in this peroxone process at higher pH value, but the extent of improvement is only slight. The optimal molar ratio of hydrogen peroxide to ozone (H2O2/O3) is 1.0, and at this condition, the mass ratio of removed COD to consumed ozone (deltaCOD/deltaO3) is twice as high as that in the ozone alone process. In the continuous peroxone process, the hydrogen peroxide addition also does not improve the ADMI removal. However, the COD removal is improved more significantly in the continuous peroxone process. The optimal H2O2/O3 molar ratio for the continuous peroxone process varies with the input liquid flow rate (QL). For liquid flow rate of 0.5 L/min, the optimal H2O2/O3 molar ratio is 3.0 and the COD removal percentage (R(COD)) reaches 50.0 to approximately 55.8%, providing about 15 min oxidation time, for the two kinds of dye solutions that were investigated in this study. The optimal residual hydrogen peroxide concentration in the working solution ([H2O2]res.) is about 1.7 x 10(-2) mol/L, providing an input rate of ozone at 8.8 x 10(-2) mol/h.
A randomized prevention trial contrasted families who took part in the Strong African American Families Program (SAAF), a preventive intervention for rural African American mothers and their 11-year-olds, with control families. SAAF is based on a contextual model positing that regulated, communicative parenting causes changes in factors protecting youths from early alcohol use and sexual activity. Parenting variables included involvement-vigilance, racial socialization, communication about sex, and clear expectations for alcohol use. Youth protective factors included negative attitudes about early alcohol use and sexual activity, negative images of drinking youths, resistance efficacy, a goal-directed future orientation, and acceptance of parental influence. Intervention-induced changes in parenting mediated the effect of intervention group influences on changes in protective factors over a 7-month period.
Longitudinal links between perceived racial discrimination and later conduct problems and depressive symptoms were examined among 714 African American adolescents who were 10-12 years old at recruitment. Data were gathered 3 times over a 5-year period. Hypotheses were tested via latent curve modeling and multiple-group latent growth modeling. Increases in perceived discrimination were associated with increased conduct problems and depressive symptoms. This association was weaker when youths received nurturant-involved parenting, affiliated with prosocial friends, and performed well academically. For conduct problems, the association was stronger for boys than for girls; for depressive symptoms, no gender differences emerged. The findings thus identify contextual variables that moderate the contribution of perceived discrimination to African American youths' adjustment.