Investigation On Premature Failure Of the Self-lubricated Piston Rings in Oil-free Compressor

Abstract: This paper presents the numerical simulation and experimental investigation on impact factors on premature failure of the self-lubricated piston rings in oil-free compressor. In this paper, the finite element method (FEM) was applied to study the non-uniform pressure distributions among the piston rings and the friction process between the self-lubricating piston rings and the cylinder wall, which influence the failure of the self-lubricated piston rings most. In order to verify the mathematic model, a test rig was built to measure the dynamic pressure distributions and temperature field between the piston rings. Both the theoretical and experimental results showed that the first piston ring afford more than 75% of the total pressure difference which was the main reason for the non-uniform wear and thus lead to early invalidation. The friction heat produced between the first piston ring and the cylinder was far more than the rest, which cannot be diffused rapidly through the low conductivity self-lubricating plastics and led to thermal failure of the self-lubricating piston rings. The results provide the theoretical basis to determine the design parameters and the thermal performance of piston rings reasonably

Study on the Effects of Vane Parameters on Separation Performance in an Axial Flow Cyclone Separator

The oil-gas cyclone separator is a key component to an oil injection compressor system for its advantages of small volume, simple structure, high separation efficiency and low pressure loss. This paper presents the investigation on new type axial flow cyclone separator performance under different structural parameters, including the angle of vanes, the number of vanes, the rotation angle of single vane, by numerical simulation and verification experiments. A numerical model of two-phase flow in the cyclone separator was established and the separation efficiency and pressure loss of cyclone separators were simulated. A test rig was built and the diameter distributions of droplets at the inlet and outlet of separator were measured by a Malvern laser particle size analyzer to verify the simulation model. The results showed that the separation efficiency and pressure loss can be improved with the increase of the rotation angle of vanes. With the decrease of the outlet angle of the first stage vane and the increase of the number of vanes, the critical separated droplet diameter of separator can be lowered effectively. The results showed that the optimum outlet angle of vanes is 22°~25° considering the separation efficiency and the pressure loss of separators

Generative Adversarial Mapping Networks

Generative Adversarial Networks (GANs) have shown impressive performance in generating photo-realistic images. They fit generative models by minimizing certain distance measure between the real image distribution and the generated data distribution. Several distance measures have been used, such as Jensen-Shannon divergence, $f$-divergence, and Wasserstein distance, and choosing an appropriate distance measure is very important for training the generative network. In this paper, we choose to use the maximum mean discrepancy (MMD) as the distance metric, which has several nice theoretical guarantees. In fact, generative moment matching network (GMMN) (Li, Swersky, and Zemel 2015) is such a generative model which contains only one generator network $G$ trained by directly minimizing MMD between the real and generated distributions. However, it fails to generate meaningful samples on challenging benchmark datasets, such as CIFAR-10 and LSUN. To improve on GMMN, we propose to add an extra network $F$, called mapper. $F$ maps both real data distribution and generated data distribution from the original data space to a feature representation space $\mathcal{R}$, and it is trained to maximize MMD between the two mapped distributions in $\mathcal{R}$, while the generator $G$ tries to minimize the MMD. We call the new model generative adversarial mapping networks (GAMNs). We demonstrate that the adversarial mapper $F$ can help $G$ to better capture the underlying data distribution. We also show that GAMN significantly outperforms GMMN, and is also superior to or comparable with other state-of-the-art GAN based methods on MNIST, CIFAR-10 and LSUN-Bedrooms datasets.Comment: 9 pages, 7 figure

Substoichiometrically Different Mitotypes Coexist in Mitochondrial Genomes of Brassica napus L

Cytoplasmic male sterility (CMS) has been identified in numerous plant species. Brassica napus CMS plants, such as Polima (pol), MI, and Shaan 2A, have been identified independently by different researchers with different materials in conventional breeding processes. How this kind of CMS emerges is unclear. Here, we report the mitochondrial genome sequence of the prevalent mitotype in the most widely used pol-CMS line, which has a length of 223,412 bp and encodes 34 proteins, 3 ribosomal RNAs, and 18 tRNAs, including two near identical copies of trnH. Of these 55 genes, 48 were found to be identical to their equivalents in the “nap” cytoplasm. The nap mitotype carries only one copy of trnH, and the sequences of five of the six remaining genes are highly similar to their equivalents in the pol mitotype. Forty-four open reading frames (ORFs) with unknown function were detected, including two unique to the pol mitotype (orf122 and orf132). At least five rearrangement events are required to account for the structural differences between the pol and nap sequences. The CMS-related orf224 neighboring region (∼5 kb) rearranged twice. PCR profiling based on mitotype-specific primer pairs showed that both mitotypes are present in B. napus cultivars. Quantitative PCR showed that the pol cytoplasm consists mainly of the pol mitotype, and the nap mitotype is the main genome of nap cytoplasm. Large variation in the copy number ratio of mitotypes was found, even among cultivars sharing the same cytoplasm. The coexistence of mitochondrial mitotypes and substoichiometric shifting can explain the emergence of CMS in B. napus

Lipopolysaccharide preconditioning enhances the efficacy of mesenchymal stem cells transplantation in a rat model of acute myocardial infarction

<p>Abstract</p> <p>Background</p> <p>Mesenchymal stem cells (MSCs)-based regenerative therapy is currently regarded as an alternative approach to salvage the acute myocardial infarcted hearts. However, the efficiency of MSCs transplantation is limited by lower survival rate of engrafted MSCs. In previous study, we found that 1.0 μg/ml Lipopolysaccharide (LPS) could protect MSCs against apoptosis induced by oxidative stress and meanwhile enhance the proliferation of MSCs. Therefore, in the present study, we firstly preconditioned MSCs with 1.0 μg/ml LPS, then transplanted MSCs into ischemic myocardium, and observed the survival and cardiac protective capacity of MSCs in a rat model of acute myocardial infarction. Furthermore, we tried to explore the underlying mechanisms and the role of Toll-like receptor-4 (TLR4) in the signal pathway of LPS-induced cardiac protection.</p> <p>Methods and results</p> <p>Acute myocardial infarction model was developed by left anterior descending coronary artery ligation. 60 rats were divided into 4 groups randomly and given an intramyocardial injection of one of the following treatments: 30 μl PBS (control group), 3 × 10⁶wild MSCs/30 μl (wMSCs group), 3 × 10⁶LPS-preconditioned wild MSCs/30 μl (LPS-wMSCs group), or 3 × 10⁶LPS-preconditioned TLR4 gene deleted MSCs/30 μl (LPS-tMSCs group). After 3 weeks, LPS-preconditioned wild MSCs transplantation ameliorated cardiac function and reduced fibrosis of infarcted myocardium. Vascular density was markedly increased in LPS-wMSCs group compared with other three groups. Survival rate of engrafted MSCs was elevated and apoptosis of myocardium was reduced in infarcted heart. Expression of vascular endothelial growth factor (VEGF) and phospho-Akt was increased in the infarcted myocardium after transplantation of LPS-preconditioned MSCs.</p> <p>Conclusion</p> <p>LPS preconditioning enhanced survival of engrafted MSCs, stimulated expression of VEGF and activated PI3K/Akt pathway. LPS preconditioning before MSCs transplantation resulted in superior therapeutic neovascularization and recovery of cardiac function. LPS preconditioning provided a novel strategy in maximizing biologic and functional properties of MSCs.</p

Evaluation of ultrasonography in fetal intestinal malrotation with midgut volvulus

Objectives: To investigate the clinical significance of prenatal diagnosis and prognostic evaluation of fetal intestinal malrotation with midgut volvulus via ultrasonography. Material and methods: Ultrasonographic findings and clinical outcomes of fetal intestinal malrotation with midgut volvulus prenatally diagnosed via ultrasound at the Zhangzhou Hospital Affiliated of Fujian Medical University from January 2013 to May 2020 were summarised and analyzed. Results: Eleven cases of fetal intestinal malrotation with midgut volvulus were accurately prenatally diagnosed according to the specific ultrasound signs, such as ‘whirlpool sign’ and ‘twining sign’. Indirect and nonspecific ultrasonographic signs included ascites in four cases and echogenic bowel in nine, all of which were accompanied by intestinal dilatation at various degrees. Among all cases, two were complicated with other system abnormalities, and one had a chromosome abnormality. Three pregnant women chose termination of pregnancy, and eight neonates were transferred to the pediatric department for surgery after obtaining written informed consent. An accurate prenatal diagnosis was confirmed postoperatively, and the fetus recovered well postoperatively. Conclusions: Fetal intestinal malrotation with midgut volvulus has typical sonographic features, and ultrasonography is the method of choice for prenatal diagnosis of this disease. Fetal intestinal malrotation with midgut volvulus is a non-fatal congenital malformation that can be treated. Prenatal diagnosis is essential for early postnatal treatment, and early surgery can often obtain good efficacy and prognosis

H9N2 Viruses Isolated From Mammals Replicated in Mice at Higher Levels Than Avian-Origin Viruses

H9N2 subtype influenza A virus (IAV) has more than 20 genotypes that are able to cross species barriers and expand from birds to mammals and humans. To better understand the impact of different H9N2 genotypes and their characteristics, five H9N2 viruses from different hosts including chickens, geese, pigs, mink, and humans representing the B69 88(Gs/14, Ck/15, and Mi/14), B35 (Sw/08) and G9 genotypes (Hu/04) were infected in chicken and mice. In mice, mammal-origin viruses replicated at higher levels in the lungs compared to avian viruses. The goose-virus replicated at the lowest levels indicating poor adaptation. Increased pro-inflammatory cytokines were positively correlated with viral loads in the lung. In chickens, all viruses were excreted from cloacal and/or oropharyngeal swabs. Interestingly, Mink-origin virus exhibited higher virulence and replication in mice and chickens. Our data indicate that mammal-origin H9N2 viruses are more adapted and virulent in mice than the avian-origin viruses

Cosmc Deficiency Causes Spontaneous Autoimmunity by Breaking B Cell Tolerance

Factors regulating the induction and development of B cell–mediated autoimmunity are not well understood. Here, we report that targeted deletion in murine B cells of X-linked Cosmc, encoding the chaperone required for expression of core 1 O-glycans, causes the spontaneous development of autoimmune pathologies due to a breakdown of B cell tolerance. BC-CosmcKO mice display multiple phenotypic abnormalities, including severe weight loss, ocular manifestations, lymphadenopathy, and increased female-associated mortality. Disruption of B cell tolerance in BC-CosmcKO mice is manifested as elevated self-reactive IgM and IgG autoantibodies. Cosmc-deficient B cells exhibit enhanced basal activation and responsiveness to stimuli. There is also an elevated frequency of spontaneous germinal center B cells in BC-CosmcKO mice. Mechanistically, loss of Cosmc confers enhanced B cell receptor (BCR) signaling through diminished BCR internalization. The results demonstrate that Cosmc, through control of core 1 O-glycans, is a previously unidentified immune checkpoint gene in maintaining B cell tolerance

A Retrospective Analysis of the Clinical Features of Inpatients With Epilepsy in the Ganzi Tibetan Autonomous Prefecture

Background: There is limited detailed clinical information for patients with epilepsy in Tibet. This study sought to provide data about the clinical features of epilepsy in the Ganzi Tibetan Autonomous Prefecture to improve strategies for epilepsy prevention and management in this region.Methods: We reviewed the clinical record of patients with epilepsy in the Neurology Department, Ganzi Tibetan Autonomous Prefecture People's Hospital and compared the clinical features and compared it with control, from West China Hospital in Chengdu.Results: This retrospective study included 165 patients with epilepsy admitted between January 2015 and February 2018. Majority of patients (97%) in this study had active epilepsy; 28.5% had generalized onset seizures and 68.5% had focal onset seizures. Fifty-four patients had received anti-epileptic drug (AED) treatment prior to hospitalization, however, 38 (70.4%) patients took the medication irregularly. The leading etiology of this cohort was head trauma (20.6%), followed by stroke (10.9%), neurocysticercosis (7.9%), brain hydatidosis (6.7%) and tuberculous infection (5.5%). Compared with in-patients in Chengdu, epilepsy in Ganzi was more frequently caused by infection (OR = 4.216, 95% CI, 2.124–8.367), including neurocysticercosis (OR = 29.301, 95% CI, 1.727–497.167) and brain hydatidosis (OR = 24.637, 95% CI, 1.439–421.670).Conclusions: These data suggest that the control of cerebral infections, especially parasite infection, is essential for the prevention of epilepsy in the Ganzi Tibetan Autonomous Prefecture. Education of local primary doctors and patients about the literacy of epilepsy will enable better management of epilepsy in this population