Performance Optimization of Parallel‐Like Ternary Organic Solar Cells through Simultaneous Improvement in Charge Generation and Transport

Ternary organic photovoltaic (OPV) devices with multiple light‐absorbing active materials have emerged as an efficient strategy for realizing further improvements in the power conversion efficiency (PCE) without building complex multijunction structures. However, the third component often acts as recombination centers and, hence, the optimization of ternary blend morphology poses a major challenge to improving the PCE of these devices. In this work, the performance of OPVs is enhanced through the morphological modification of nonfullerene acceptor (NFA)‐containing binary active layers. This modification is achieved by incorporating fullerenes into the layers. The uniformly dispersed fullerenes are sufficiently continuous and successfully mediate the ordering of NFA without charge or energy transfer. Owing to the simultaneous improvement in the charge generation and extraction, the PCE (12.1%) of these parallel‐linked ternary devices is considerably higher than those of the corresponding binary devices (9.95% and 7.78%). Moreover, the additional energy loss of the ternary device is minimized, compared with that of the NFA‐based binary device, due to the judicious control of the effective donor:acceptor composition of the ternary blends.     

Gelation properties of partially renneted milk

Acid- and rennet-induced gelation properties of milk with modified casein micelles, produced by partial renneting at 4^oC for 15 min, followed by inactivation of enzymes by heat at 60^oC/3 min (referred as low heat treatment milk) and 85^oC/30 min (high heat treatment milk), were investigated to provide a mechanistic understanding of gel formation from partially renneted milk. Acidification of low heat treatment milk gave firmer gel quality, this was reflected by its high elastic modulus (G′) and hardness. In addition, the high heating condition for enzyme inactivation of high heat treatment milk alone increased the elastic modulus of both the control and renneted milk samples. Gel development of the two milk types (low heat treatment and high heat treatment milks) was different. In contrast with acid gelation, rennet-induced gelation of partially pre-rennet treated milk had no impact on the elastic modulus of low heat treatment milk and the rennet gels were very weak. Similarly, the addition of rennet to pre-rennet treated high heat treatment milk did not produce “true gels,” most likely due to the effect of the heat treatment on impairing the rennet coagulation. The findings in this study confirmed that pre-rennet treated milk had positive effects on the end-product acid gels of low heat treatment and high heat treatment milk.     

Effects of milk pH alteration on casein micelle size and gelation properties of milk

The effects of changes in pH above and below the natural pH of milk (ca 6.6) on the casein micelle size and the gelation properties of the pH adjusted and restored samples were investigated. The size of casein micelles increased at pH 7.0 and 7.5, then started to decrease above pH 8.5. It is postulated that at pH below 8.5 the casein micelles swell, while elevated pH causes their dissociation. Conversely, the size of casein micelles decreased on acidification to pH 5.5 and increased when the pH dropped below 5.5, due to the shrinkage of casein micelles at lower pH before their aggregation at pH below 5.5. In response to neutralising treated milk back to normal milk pH of 6.6, it was found that the casein micelle size of treated milk with a narrow range of pH change between 6.0 and 7.0 was reversible, while beyond this range the structure of casein micelles became irreversible. The restoration of casein micelle size was followed by the restoration of some parameters such as soluble calcium, ethanol stability, and milk whiteness. Acid-induced gelation did not change the elastic modulus, while rennet-induced gelation was affected by initial milk pH. In reference to the size of reversible range elastic modulus (G’) of acid or rennet gels made from restored milk, the sizes were similar to control milk after 6 h of gelation.     

Thermal effects in suspended RF spiral inductors

Self-heating effects on integrated suspended and bulk spiral inductors are explored. A dc current is fed through the inductors during measurement to emulate dc and radio frequency power loss on the inductor. A considerable drop in Q by /spl sim/18% at 36.5 mW is observed for suspended coils with 3-/spl mu/m aluminum metallization compared to reference inductors on bulk-Si. Simulations in Ansoft's ePhysics indicate that, due to the thermal isolation of the suspended coil, the power loss from resistive self-heating in the metal has to be transferred outwards through the metal turns. This also results in a thermal time constant. This time constant is measured to be /spl sim/10 ms, meaning that it can affect power circuits operating in pulsed mode.     

Optimal cut-off for obesity and markers of metabolic syndrome for Ethiopian adults

Background

Metabolic syndrome (MetS) is defined as the presence of central obesity plus any two of the following markers: high triglycerides (>?150 mg/dl), low high density lipoprotein (HDL) cholesterol <?40 mg/dl in men and?<?50 mg/dl in women, hypertension (blood pressure?>?130/85 mmHg or use of antihypertensive medication), high fasting blood glucose (>?100 mg/dl or use of treatment for diabetes mellitus). Since recently, metabolic syndrome and obesity have become emerging problems of both low and middle income countries, although they have been the leading cause of morbidity and mortality in high income countries for the past decades. It has been indicated that the international anthropometric cut-off for detecting obesity is not appropriate for Ethiopians. This study developed optimal cut off values for anthropometric indicators of obesity and markers of metabolic syndrome for Ethiopian adults to enhance preventive interventions.

Methods

A total of 704 employees of Jimma University were randomly selected using their payroll as a sampling frame. Data on socio-demographic, anthropometry, clinical and blood samples were collected from February to April 2015. Receiver Operating Characteristic Curve analyses were used to determine optimal anthropometric cut-off values for obesity and markers of the metabolic syndrome. WHO indicators of obesity based on body fat percent (>?25% for males and?>?35% for females) were used as binary classifiers for developing anthropometric cut-offs. Optimal cut-off values were presented using sensitivity, specificity and area under the curve.

Results

The optimal cut-off for obesity using body mass index was 22.2 k/m² for males and 24.5 kg/m² for females. Similarly, the optimal waist circumference cut-off for obesity was 83.7 cm for males and 78.0 cm for females. The cut-off values for detecting obesity using waist to hip ratio and waist to height ratio were: WHR (0.88) and WHtR (0.49) for males, while they were 0.82 and 0.50 for females, respectively. Anthropometric cut-off values for markers of metabolic syndrome were lower compared to the international values. For females, the optimal BMI cut-offs for metabolic syndrome markers ranged from 24.8 kg/m² (triglycerides) to 26.8 kg/m² (fasting blood sugar). For WC the optimal cut-off ranged from of 82.1 cm (triglyceride) to 96.0 cm(HDL); while for WHtR the optimal values varied from 0.47(HDL) to 0.56(fasting blood sugar). Likewise, the optimal cut-offs of WHR for markers of metabolic syndrome ranged from 0.78(fasting blood sugar) to 0.89(HDL and blood pressure). For males, the optimal BMI cut-offs for metabolic syndrome markers ranged from 21.0 kg/m² (HDL) to 23.5 kg/m² (blood pressure). For WC, the optimal cut-off ranged from 85.3 cm (triglyceride) to 96.0 cm(fasting blood sugar); while for WHtR the optimal values varied from 0.47(BP, FBS and HDL) to 0.53(Triglyceride). Similarly, the optimal cut-offs of WHR form markers of metabolic syndrome ranged from 0.86(blood pressure) to 0.95(fasting blood sugar).

Conclusion

The optimal anthropometric cut-offs for obesity and markers of metabolic syndrome in Ethiopian adults are lower than the international values. The findings imply that the international cut-off for WC, WHtR, WHR and BMI underestimate obesity and metabolic syndrome markers among Ethiopian adults, which should be considered in developing intervention strategies. It is recommended to use the new cut-offs for public health interventions to curb the increasing magnitude of obesity and associated metabolic syndrome and diet related non-communicable diseases in Ethiopia.