EXTRACTION, FRACTIONATION AND ACTIVITY CHARACTERISTICS OF PROTEASES FROM SHRIMP PROCESSING DISCARDS

Proteases recovered from Northern pink shrimp (NPS) and Southern rough shrimp (SS) processing discards (heads, shells, tails) were characterized. Shrimp processing discards were extracted with water following homogenization and centrifugation in order to obtain the crude extract which was subsequently fractionated with solid ammonium sulfate. Two fractions sedimenting with 30–50% (designated as NPS‐I and SS‐I), and 50–70% (designated as NPS‐II and SS‐II) ammonium sulfate were collected following centrifugation, respectively. Endoprotease activity of the crude extract was 0.02 U/mg for hemoglobin (Hb, pH 3.0), 0.16 U/mg for azocasein (Ac, pH 6.0) and 0.12 U/mg for benzoyl‐Arg‐β‐naphthylamide (BANA, pH 7.0). The exoprotease activity was 0.11–0.17 U/mg for Arg‐β‐naphthylamide (ArgNA, pH 7.0), 0.06–0.11 U/mg for Lys‐β‐naphthylamide (LysNA, pH 7.0) and 0.08–0.09 U/mg for Leu‐β‐naphthylamide (LeuNA, pH 7.0). Endoprotease activity increased 5–7.4 fold for NPS‐I and SS‐I, and 1.9–2.7 fold for NPS‐II and SS‐II against crude extract. Meanwhile, exoprotease activity increased 3.6–4.8 fold for NPS‐I and SS‐I, and 5.6–7.2 fold for NPS‐II and SS‐II. Meat treated with NPS‐I and SS‐I was tenderized more extensively than that treated with NPS‐II and SS‐II. The results of this study suggest that proteases recovered from shrimp processing discards may potentially be used as processing aids in formulated foods.     

Heat transfer characteristics of nanofluid through circular tube

Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300相似文献   

PIEZOELECTRIC PROPERTIES OF ((Na0.5K0.5)1−xLix)(Nb0.8Ta0.2)O3 CERAMICS

ABSTRACT

In the ((Na_0.5K_0.5)_1?x)Li_x)(Nb_0.8Ta_0.2)O₃ (NKLNT) system, dense ceramics were developed by conventional sintering process. The electrical properties of NKLNT ceramics were investigated as a function of Li substitution. When the sample sintered at 1100°C for 4 h with the substitution of 2 mol% Li at the morphotropic phase boundary, electro-mechanical coupling factor (k_P) and piezoelectric coefficient (d₃₃) were found to reach the highest values of 0.42 and 210 pC/N, respectively. These excellent piezoelectric and electromechanical properties indicate that this system is potentially good candidate for lead-free material for a wide range of electro-mechanical transducer applications.     

Dielectrophoretic assembly of semiconducting single-walled carbon nanotube transistor

A novel burning technique for making a semiconducting single-walled carbon nanotubes (SWNTs) transistor assembled by the dielectrophoretic force was suggested. The fabrication process consisted of two steps. First, to align and attach a bundle of SWNTs between the source and drain, the alternating (AC) voltage was applied to the electrodes. When a bundle of SWNTs was connected between two electrodes, some of metallic nanotubes and semi-conducing nanotubes existed together. The second step is to burn the metallic SWNTS by applying the voltage between two electrodes. With increasing the voltage, more current flowed through the metallic SWNTs, thus, the metallic SWNTs burnt earlier than the semiconducting one. This technique enables to obtain only semi-conducting SWNTs connection in the transistor. Through the I—V characteristic graph, the moment of metallic SWNTs burning and the characteristic of semi-conducing nanotubes were verified.