Study on pulse current auxiliary heating process of submerged arc welding.

During the welding process, temperature filed distribution of weldment is one of the key factors which influence welding quality. In order to improve the mechanical properties of welding joint, a technology for heating process of weldment using auxiliary pulse current was proposed in this article. Firstly, through metallographic experiment, strength experiment and hardness experiment, it was proved that the auxiliary pulse current not only can refine grain size but also improves the mechanical property of the welding joint. Then the paper used ANSYS and its ANSYS Parametric Design Language parametric design language to simulate the welding process with assistant pulse current, and the temperature field, the pulse current density distribution and the time of effective pulse current in the welded joint were obtained. Quantitative analyses were undertaken on the influence laws of auxiliary pulse current parameters on weld temperature field, auxiliary pulse current density distribution and the time of effective pulse current. A new parameter was defined as time-current density (the time integral of current density) to demonstrate the change rule of auxiliary pulse current density distribution with time. Finally, analyzing the reasons for raising the welding quality. There were two reasons for such phenomenon: one was auxiliary pulse current change the state of heat distribution in the weld seam area, the other was that the impulse oscillation of the auxiliary pulse influences the nucleation process of melting region.

Formation of iodinated aromatic DBPs at different molar ratios of chlorine and nitrogen in iodide-containing water.

Variations in iodinated aromatic disinfection byproducts (DBPs) in the presence of I- and organic compounds as a function of reaction time in different molar ratios (MRs) of HOCl:NH3-N were investigated. Up to 17 kinds of iodinated aromatic DBPs were identified in the breakpoint chlorination of iodide (I-)/organic (phenol, bisphenol S (BPS) and p-nitrophenol (p-NP)) systems, and the possible pathways for the formation of iodinated aromatic DBPs were proposed. The reaction pathways include HOCl/HOI electrophilic substitution and oxidation, while the dominant iodinated DBPs were quantified. In the I-/phenol system (pH = 7.0), the sum of the concentrations of four iodinated aliphatic DBPs ranged from 0.32 to 1.04 µM (triiodomethane (TIM), dichloroiodomethane (DCIM), diiodochloromethane (DICM) and monoiodoacetic acid (MIAA)), while the concentration of 4-iodophenol ranged from 2.99 to 12.87 µM. The concentration of iodinated aromatic DBPs remained stable with an MR = 1:1. When the MR was 6:1, iodinated aromatic DBPs decreased with increasing reaction time, in which the main disinfectant in the system was active chlorine. This study proposed the formation mechanism of iodinated aromatic DBPs during the breakpoint chlorination of iodide-containing water. These results can be used to control the formation of hazardous iodinated aromatic DBPs in the disinfection of iodine containing water.

[Total flavonoids of Drynariae Rhizoma regulates ER-p38 MAPK signaling pathway to improve scopolamine-induced learning and memory impairments in model mice].

This study intended to explore the effect and mechanism of total flavonoids of Drynariae Rhizoma in improving scopola-mine-induced learning and memory impairments in model mice. Ninety four-month-old Kunming(KM) mice were randomly divided into six groups. The ones in the model group and blank group were treated with intragastric administration of normal saline, while those in the medication groups separately received the total flavonoids of Drynariae Rhizoma, Kangnaoshuai Capsules, donepezil, as well as total flavonoids of Rhizoma Drynariae plus estrogen receptor(ER) blocker by gavage. The mouse model of learning and memory impairments was established via intraperitoneal injection of scopolamine. Following the measurement of mouse learning and memory abilities in Morris water maze test, the hippocampal ERß expression was detected by immunohistochemistry, and the expression levels of ERß and phosphorylated p38(p-p38) in the hippocampus and B-cell lymphoma 2(Bcl-2), Bcl-2-associated death promoter(Bad), and cysteinyl aspartate-specific protease-3(caspase-3) in the apoptotic system were assayed by Western blot. The contents of malondia-ldehyde(MDA), superoxide dismutase(SOD), and nitric oxide(NO) in the hippocampus were then determined using corresponding kits. Compared with the control group, the model group exhibited significantly prolonged incubation period, reduced frequency of cros-sing the platform, shortened residence time in the target quadrant, lowered ERß, Bcl-2 and SOD activity in the hippocampus, and increased p-p38/p38, Bad, caspase-3, MDA, and NO. Compared with the model group, the total flavonoids of Rhizoma Drynariae increased the expression of ERß and SOD in the hippocampus, down-regulated the expression of neuronal pro-apoptotic proteins, up-re-gulated the expression of anti-apoptotic proteins, and reduced p-p38/p38, MDA, and NO. The effects of total flavonoids of Drynariae Rhizoma on the above indexes were reversed by ER blocker. It has been proved that the total flavonoids of Drynariae Rhizoma obviously alleviate scopolamine-induced learning and memory impairments in mice, which may be achieved by regulating the neuronal apoptotic system and oxidative stress via the ER-p38 mitogen-activated protein kinase(ER-p38 MAPK) signaling pathway.

Study on microwave assisted extraction of chrysophanol and its intervention in biofilm formation of Streptococcus suis.

A microwave assisted extraction technology was used to extract chrysophanol from rhubarb. The present study will focus on the optimum extraction conditions of chrysophanol and discuss the inhibitory effect of chrysophanol on the biofilm formation of Streptococcus suis (S. suis). A Box-Behnken design based on single-factor experiments was applied to optimize the microwave assisted extraction process and to study the factors' relationships with each other. The results showed that a microwave temperature of 56 °C, ethanol concentration of 70%, microwave power of 540 W and liquid to raw material ratio of 55 mL g-1 were the optimal conditions for the microwave method. The yield of chrysophanol was 2.54 ± 0.07% under the optimal conditions, which was in agreement with the predicted value (2.64%). Then, the chemical structure of the extracted chrysophanol was identified by LC-MS. In addition, in vitro experiments showed that chrysophanol has an inhibitory effect on S. suis (minimum inhibitory concentration was 1.98 µg mL-1) and was shown to significantly inhibit the capability of S. suis to form a biofilm using crystal violet staining. Finally, scanning electron microscopy analysis showed that the three-dimensional structure of the biofilm deposited by the S. suis community was destroyed by chrysophanol.