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Throughout history, the progress of human society has been propelled by continuous accumulation of experience. People distill patterns and rules out of their experience that contribute to broader applicability. This is how preliminary theories are formulated. The preliminary theory can further develop in two directions. One is to use the theory for practical applications such as to increase agricultural output, to invent new medical instruments and to raise production of electric appliances. The other direction is to explore ultra microstructures and to uncover the fundamentals of natural phenomena, resulting in further development of the theory. In the fi rst case, incremental improvements are possible without revamping the theoretical foundation. However, theoretical breakthroughs are required for major innovations such as development of jumbo jets, operation of high speed rails and manufacture of nuclear powered aircraft carriers. In the case of today’s pure theory sciences such as archaeology, geophysics and ecological studies, as people become more knowledgeable about the world, it is possible for these theories to gradually reveal their practical implications and guide human practice to advance social development.

Faced with the end stage of heart disease, the current treatments only slow worsening of heart failure. Stem cells have the potential of self-renewal and differentiation. It is expected to replace and repair damaged myocardium. But many clinical trials have shown that the stem cell therapy of heart failure is modest or not effective. The possible causes for the limited effects of stem cell in curing heart failure are the stem cells which have been transplanted into the ischemic heart muscle may suffer low survival rate, affected by inflammatory molecules, proapoptotic factor, and lack of nutrients and oxygen, and then the stem cells which home and have been completely transplanted to the site of myocardial infarction become very small. Therefore, through preconditioning of stem cells and appropriate choice of genes for mesenchymal stem cell modification to improve the survival rate of stem cells, ability in homing and promoting angiogenesis may become the newly effective strategies for the application of stem cells therapy in heart failure.

The materials with grain size gradient variation on the surface, which were prepared with mechanical-induced severe plastic deformation, always show high resistance to high and low cycle fatigue and frictional wear because of their good strength–ductility synergy. The ultrasonic surface rolling treatment (USRT) has the advantages of high processing efficiency, good surface quality, and large residual compressive stress introduced to the surface after treatment. The USRT was used to prepare aluminum alloy (AA7075) samples with a surface gradient structure; meanwhile, the microstructural evolution mechanism of the deformation layers on the gradient structure was studied with XRD, SEM, and TEM. The microstructure with gradient distribution of grain size and dislocation density formed on the surface of AA7075 aluminum alloy after USRT. The surface layer consists of nanocrystals with random orientation distribution, and high-density dislocation cells and subgrains formed in some grains in the subsurface layer, while the center of the material is an undeformed coarse-grained matrix. The results show that the dislocation slip dominates the grain refinement process, following the continuous cutting and refinement of dislocation cells, subgrains, and fragmentation of the second precipitates. This study systematically clarified the mechanism of grain refinement and nanocrystallization on the surface of high-strength aluminum alloys and laid a theoretical foundation for further research on mechanical behavior and surface friction and wear properties of high-strength non-ferrous materials with gradient structure. [ABSTRACT FROM AUTHOR]

To reveal the effects of confinement and curvature on the jet mixing in a supersonic cross-flow, large eddy simulations were conducted to study the jet in supersonic cross-flow in a channel and a pipe at a Mach number of 2.7. The comparison was based on an equal friction Mach number, friction Reynolds number, and Prandtl number. The synthetic eddy model was utilized to generate the inflow turbulent boundary layer. Our study shows the major counter-rotating vortex pair (CVP) was higher in the pipe than in the channel, while the trailing CVP was larger and appeared within the recirculating flow. The pipe had a stronger shock train than the channel due to the confinement and curvature of the pipe. The jet penetration of the pipe is 18.4% larger than that of the channel at x / D = 10, and the stream velocity of the pipe is much more reduced behind the jet than in the channel. Three reasons for the higher mixing efficiency of the pipe are revealed according to our findings, including the larger and higher major CVP, the higher penetration, the stronger shock. The mixing efficiency of the pipe is 4.68% higher than that of the channel due to the above reasons at x / D = 10. [ABSTRACT FROM AUTHOR]

The oral and upper respiratory tracts are closely linked anatomically and physiologically with the lower respiratory tract and lungs, and the influence of oral and upper respiratory microbes on the lung microbiota is increasingly being recognized. However, the ecological process and individual heterogeneity of the oral and upper respiratory tract microbes shaping the lung microbiota remain unclear owing to the lack of controlled analyses with sufficient sample sizes. Here, the microbiomes of saliva, nasal cavity, oropharyngeal area, and bronchoalveolar lavage samples are profiled and the shaping process of multisource microbes on the lung microbiota is measured. It is found that oral and nasal microbial inputs jointly shape the lung microbiota by occupying different ecological niches. It is also observed that the spread of oral microbes to the lungs is heterogeneous, with more oral microbes entering the lungs being associated with decreased lung function and increased lung proinflammatory cytokines. These results depict the external shaping process of lung microbiota and indicate the great value of oral samples, such as saliva, in monitoring and assessing lung microbiota status in clinical settings. [ABSTRACT FROM AUTHOR]

Background: Trauma especially head trauma is considered a potential risk factor of amyotrophic lateral sclerosis (ALS), but their association has not been well established. We aimed to determine the association of prior trauma with ALS risk. Methods: This study was performed according to the Meta-Analysis of Observational Studies in Epidemiology guideline to assess related literatures, and a random-effects model was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Results: Twenty-nine eligible articles involving 18,390 cases and 6,519,391 controls were included in this meta-analysis. The results showed that trauma was associated with an increased risk of ALS (pooled OR = 1.51, 95% CI: 1.32–1.73). Besides, patients with trunk trauma, head trauma and lower limb trauma had an increased risk of ALS, whereas no evidence suggested that upper limb trauma and spine trauma could increase ALS risk. Considering the number of traumatic events, the association between trauma and ALS risk was significant for patients with repeated trauma events (pooled OR = 1.21, 95% CI: 1.07–1.38). The results showed that individuals with a history of trauma within 5 years were more likely to be diagnosed with ALS (pooled OR = 1.84, 95% CI: 1.56–2.17). Importantly, both old trauma and very old trauma were found to be associated with an increased risk of ALS (pooled OR = 1.24, 95% CI: 1.12–1.38; pooled OR = 1.28, 95% CI: 1.10–1.49; respectively). Conclusions: This meta-analysis indicated that trauma could increase ALS risk, which may be applied for the clinicians to tailor targeted treatment regimens and make prophylactic strategies for ALS in traumatic patients. [ABSTRACT FROM AUTHOR]

Background: Prior studies have suggested that head injury might be a potential risk factor of amyotrophic lateral sclerosis (ALS). However, the association has not been well established. We aimed to provide a synopsis of the current understanding of head injury's role in ALS. Methods: We performed a systematic search in PubMed for observational studies that quantitatively investigated the association between head injury and ALS risk published before April 10, 2020. We used a random-effects model to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Results: Fourteen eligible articles including 10,703 cases and 2,159,324 controls were selected in current meta-analysis. We found that head injury was associated with an increased risk of ALS (OR = 1.38, 95% CI: 1.20–1.60) and the association was slightly stronger concerning severe head injury and ALS risk (OR = 1.69, 95% CI: 1.27–2.23). Considering the number of head injuries (N) and ALS risk, the association was weak (OR = 1.23, 95% CI: 1.10–1.37, N = 1; OR = 1.29, 95% CI: 0.89–1.86, N ≥ 2). In addition, a strong association with ALS risk was found in individuals who suffered head injury <1 year (OR = 4.05, 95% CI: 2.79–5.89), and when the time lag was set at 1–5, 5–10, and >10 years, the pooled OR was 1.13, 1.35, and 1.10, respectively. Conclusion: This meta-analysis indicates that head injury, especially severe head injury, could increase ALS risk. Although a strong association is found between head injury <1 year and ALS risk in the current study, this result suggests a possibility of reverse causation. [ABSTRACT FROM AUTHOR]