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Acute lung injury (ALI) is a life-threatening clinical condition associated with critically ill patients, and the construction of potential microRNA (miRNA) and messenger RNA (mRNA) regulatory networks will help to fully elucidate its underlying molecular mechanisms. First, we screened fifteen upregulated differentially expressed miRNAs (DE-miRNAs) and six downregulated DE-miRNAs from the Gene Expression Omnibus (GEO) database. Then, the predicted target genes of the upregulated and downregulated DE-miRNAs were identified from the miRNet database. Subsequently, differentially expressed mRNAs (DE-mRNAs) were identified from the GEO database and subjected to combined analysis with the predicted DE-miRNA target genes. Eleven target genes of the upregulated DE-miRNAs and one target gene of the downregulated DE-miRNAs were screened out. To further validate the prediction results, we randomly selected a dataset for subsequent analysis and found some accurate potential miRNA-mRNA regulatory axes, including mmu-mir-7b-5p-Gria1, mmu-mir-486a-5p-Shc4 and mmu-mir-486b-5p-Shc4 pairs. Finally, mir-7b and its target gene Gria1 and mir-486b and its target gene Shc4 were further validated in a bleomycin-induced ALI mouse model. We established a potential miRNA-mRNA regulatory network of ALI in mice, which may provide a basis for basic and clinical research on ALI and advance the available treatment options. [ABSTRACT FROM AUTHOR]

The profile of drill flute has a great influence on the drilling performance of micro-drill. It is promising to obtain a desired flute profile with a standard wheel by adjusting the wheel position parameters during the grinding process. To investigate the flute profile characteristics under different wheel position parameters and its effect on the drilling performance, this paper presents a method for modeling and optimization of the micro-drill flute considering the wheel installation angle and the offset distance from the wheel origin to the drill blank origin. Based on this model, the flute profile of micro-drill is numerically simulated by MATLAB software firstly, and then, the 3D model of micro-drill with different flute profiles is established by UG software. Finally, the micro-drilling process on 304 austenitic stainless steel is simulated by DEFORM software, and the chip morphology and the drilling force are analyzed and discussed. The results show that the wheel installation angle has an obvious effect on the flute profile and its radial rake angle and flute width, and the wheel offset distance only influences the flute width evidently. The micro-drill with flute ground by smaller wheel installation angle owns straighter cutting lip shape and larger chip evacuation capacity, and its thrust force and torque are smaller than those of other micro-drills. Moreover, spiral chip is generated due to the intense side curl and up curl of the chip, resulting in the easiness of the chip removal. However, for the micro-drills with flute ground by larger wheel installation angle, the chip morphology is string and the drilling force is larger. At last, the mathematical model of the drill flute and its numerical simulation result are validated by experimentally fabricating the micro-drill flute. Then, the optimized micro-drill is manufactured by a six-axis computer numerical control (CNC) grinding machine, and its flute profile is fabricated using a standard conical grinding wheel with a smaller wheel installation angle. [ABSTRACT FROM AUTHOR]

Micro end milling is a main method for the fabrication of microgroove parts which are widely applied in biology, electronics, precision machinery, and other fields. However, the machining quality of microgroove is difficult to meet requirements due to size effect, and the machined grooves easily produce high surface roughness and poor form accuracy during micro milling. In this paper, in order to investigate the effects of machining inclination angles on the performance of micro ball end milling, the micro milling experiments on Ti-6Al-4V are carried out by setting the micro ball end mill with different inclination angles in feed direction, cross-feed direction, and the combination of the two directions, respectively. The results show that the tool orientation strategy has significant influences on the quality of microgroove and can reduce the roughness and improve the form accuracy. With increase of the absolute value of inclination angle along feed direction from 0° to 45°, the surface roughness has a decreasing trend, and the chips adhesion and texture becomes inconspicuous. When inclination angle along feed direction is 30° and 45°, the combination inclination angle strategy has no obvious influences on the surface roughness with increase of inclination angle along cross-feed direction. However, the combination inclination angles strategy can reduce the maximum form deviation and improve the form accuracy of the groove. Based on the results, an optimal combination inclination angles with feed direction 45° and cross-feed direction 20° strategy is proposed to machining the microgroove. [ABSTRACT FROM AUTHOR]

Helical drill point is characterized by a continuous helical flank surface and an S-shape chisel edge, and its special geometry contributes to a superior drilling performance and a better grinding efficiency. However, the existing grinding processes are complicated and hard to be reproduced in practice, and it is difficult to meet the accuracy requirements as the drill diameter becomes smaller. Thus, it is crucial to research further grinding method of helical micro-drill and its drilling performance. In this paper, a grinding method of helical drill flank using a six-axis CNC grinding machine is proposed based on the mathematical model of generatrix of the helical surface. Then, this grinding process is simulated using the 3D CAD software and is validated by experimentally fabricating the helical micro-drill. The results show that this method is feasible for obtaining the micro-drill with high dimensional accuracy. For the comparison with helical micro-drill, the planar and conical micro-drills with the same geometry parameters are produced as well. The drilling experiments on 1Cr18Ni9Ti austenitic stainless steel with the planar, conical, and helical micro-drills are conducted, and the drilling force, tool wear, and hole quality are measured and analyzed. The experiment results show that the increasing rate of the radial force of helical micro-drills at the beginning of the drilling process is smaller than those of planar and conical micro-drills, the thrust force and wear of helical drill point are also smaller, and the quality of micro-holes by helical drill point is better as well. It is confirmed that the proposed grinding process is effective to fabricate the helical micro-drill with good drilling performance. [ABSTRACT FROM AUTHOR]