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The continuous smooth derivable principle of micro-convex asperity contact surface within the elastic, elastic-plastic and plastic contact deformations is applied to demonstrate the contact strength and the continuity and regional disparity of the practical contact surfaces under loading. A bolt structure model is established using the mixed-element method, and the practical contact area and the contact stress distribution are solved. The predicted results from finite element analysis(FEA) are highly correlated with the ones obtained from ultrasonic physical tests. The correctness and validity of the model are verified. The transmission effect of stress along the bolt joint direction is investigated through series of models, the continuity of the contact stress of the bolt joint in the annular region is further proved, and the effect laws of changing the pretightening force and structure geometric parameters on the bolt joint contact strength and the range of contact stress are discussed. [ABSTRACT FROM AUTHOR]

To investigate the expression pattern of lipogenic genes in mammary gland of mouse in different lactation stages, the relative mRNA abundance and expression of 20 genes involved in milk fat synthesis and secretion of lactating mammary tissues were assessed using real-time PCR. Results revealed the significant upregulation of mRNA expression for both high abundant genes (abundance > 5%), such as LPL, ACACA, SCD, XDH, BTN, and ADFP and moderate abundant genes (5% > abundance > 1%), such as CD36, FASN, AGPAT6, and DGAT in lactation stages compared to pregnancy (P < 0.05). The mRNA expression of lipogenic enzyme genes for ACACA, SCD, FASN, AGPAT6, and DGAT exhibited lower expression lever in early (6 d) and late (18 d) lactation stages but higher expression level at middle stage (12 d), demonstrating a low-high-low pattern. Besides, the mRNA levels of some gene regulators were also measured. The mRNA expression of SREBF gene increased gradually along with the lactation, which showed a 10-fold elevation at middle stage (12 d). The expression pattern of SREBF gene was the same as lipogenic enzyme genes, suggesting that SREBF may play an important role in the regulation of lipogenic enzyme genes in the lactating mammary gland.

Objective: To observe changes of learning and memory ability (LMA) in burn rats with depression, and study the relationship between LMA and expression of hippocampal NMDA., Methods: According to simple random method, 46 Wistar rats were divided into burn group (B, with 30% TBSA deep partial-thickness burn, n = 10), depression group (D, with moderate stress stimulation in chronic and unpredictable, n = 12), B + D group (with the same stress stimulation inflicted to B group after burn, n = 12), healthy control group ( HC, without treatment, n = 12). Changes in escape latency was examined in water maze test. Expression of hippocampal NMDA in CA1, CA2 regions and dentate gyrus were observed with immunohistochemistry., Results: Compared with that of HC group (22 +/- 20 s), water maze escape latency in B, D, B + D groups on 2 day after training prolonged (38 +/- 31, 41 +/- 36, 42 +/- 33 s, respectively, P < 0.05 or P < 0.01). Water maze escape latency in B + D group on 4th day after training was longer than that of other groups (P < 0.01). There was no obvious difference in positive expression of NMDA in CA1, CA2 regions among groups (P > 0.05). The positive count of NMDA in dentate gyrus in D group (198 +/- 14) and B + D group (191 +/- 6) were lower than that of HC group (224 +/- 23, P < 0.05 or P < 0.01), but there was no obvious difference between HC group and B group (219 +/- 25, P > 0.05)., Conclusions: Burn complicated with depression can reduce LMA, which may be due to a decrease in NMDA in dentate gyrus.