In the present study, six diets were formulated to contain 24% or 36% protein, and 0, 20%, or 40% starch. The Nile tilapias (Oreochromis niloticus) were fed with the designed diets for 56 days. An overall increasing tendency of percent weight gain, feed efficiency, protein efficiency rate (PER), hepatosomatic index (HSI), and condition factor (CF), whole-body protein and lipid contents, plasma concentrations of triglyceride (TG), total cholesterol (T-CHO) and glucose, liver glycogen contents, liver activities of glucokinase, pyruvate kinase, fatty acid synthetase, lipoprotein lipase (LPL), glucose-6-phosphate dehydrogenase, and malic enzyme with increasing dietary starch level was noted. While the opposite trend was found for feed intake (FI), whole-body moisture and ash contents, liver activities of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK). Furthermore, all the parameters above were higher in fish fed the 36% vs. 24% protein diets, expect FI, PER, whole-body moisture, liver G6Pase and PEPCK were opposite, and furthermore HSI, whole-body lipid, liver glycogen and LPL were unaffected by dietary protein treatments. The results indicate that Nile tilapia appears to have a more sensitive response to dietary starch level than dietary protein level. Appropriate dietary starch supplementation could help promote the growth of the fish species. Low-dietary protein (24%) allowance may acquire growth comparable to that of Nile tilapia fed 36% protein diets when feed protein is provided only by fish meal with at least 20% starch supplementation. ARTICLE HISTORY

Manipulation of underwater bubbles is of great importance in both scientific research and industrial applications. In this work, the motion of underwater bubbles on a microholed polydimethylsiloxane (PDMS) surface with gradient wettability is studied using a high-speed camera. It was found that underwater bubbles self-transported directionally from the smaller area fraction (SAF) to the larger area fraction (LAF) of the surface. Besides, the bubble motion was triggered by an effective depth range from hcr,min to hcr,max. Only the depth of the bubble was within the range when the self-transport motion occurred. Otherwise the bubble would adhere onto the surface eventually. The main cause for the motion is the trapped air inside the microholes, which generates the torque Tb and the retention force Fr driving the bubble directionally. The mathematical model is established to reveal the motion mechanism, which is verified by the experimental results. The outcomes of our work shed new light on the target transportation fields such as drug delivery and submarine gas collection.

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A feeding trial was conducted in tilapia to determine the growth performance, nutrient digestibility, digestive enzymes, and postprandial blood metabolites in response to different dietary amylose-amylopectin ratios. Five isonitrogenous and isolipidic diets containing an equal starch level with different amylose-amylopectin ratios of 0.11 (diet 1), 0.24 (diet 2), 0.47 (diet 3), 0.76 (diet 4) and 0.98 (diet 5) were formulated using high-amylose corn starch (as the amylose source) and waxy rice (as the amylopectin source). Each diet was hand-fed to six tanks of 15 fish each, three times a day over a 6-wk period. After the growth trial, a postprandial blood metabolic test was carried out. Fish fed diet 2 exhibited the highest percent weight gain and feed efficiency and protein efficiency ratio, whereas fish fed with diet 5 showed the lowest growth and feed utilization among treatments. The digestibility for starch in fish fed diet 1 and 2 was higher than those in fish fed with other diets (p<0.05). The highest activities for protease, lipase and amylase were found in fish fed the diet 2, diet 1, and diet 1 respectively among dietary treatments, while the lowest values for these indexes were observed in fish fed the diet 3, diet 5 and diet 4, respectively. The liver glycogen concentrations in fish fed diets 4 and 5 were found higher than in fish fed other diets (p<0.05). The feeding rate, hepatosomatic index, condition factor, and plasma parmeters (glucose, triglyceride, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol) did not differ across treatments. In terms of postprandial blood responses, peak blood glucose and triglycerides were lower after 3 or 6 h in the fish fed with diets 3–5 than in the fish fed diet 1, but delayed peak blood total amino acid time was observed in fish fed with the diets 1 or 2. The lowest peak values for each of the three blood metabolites were observed in fish fed diet 5. The results indicate that high-dietary amylose-amylopectin ratio could compromise growth, but help in reducing the blood glucose stress on fish caused by postprandial starch load.

We investigate the self-propelled motion of the Leidenfrost droplets on hot surfaces with ratchet like topology. It is found that on hot ratchet surfaces with the certain geometry parameters, the droplets move in the direction towards the steep side of the teeth; as the surface temperature rises, droplets are observed to self propel to the right-angle side direction. Furthermore, there exists a temperature threshold to trigger the motion, at which the droplets do not move in either direction but stay at the stagnation state. A physical model is proposed to analyze the observation in this paper.

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