Solid rocket motor propellant health monitoring based on oxide-doped curved long-period fiber grating.

A kind of curved long-period fiber grating(CLPFG) engraved by CO2 laser based on oxide-doped fiber was designed to monitor the structural integrity of propellant. The mechanical damage characteristics of the propellant were analyzed. The sensor model is constructed and the refractive index modulation characteristics of the CLPFG are analyzed. The strain coupling characteristics and the strain transfer efficiency of the interface between the CLPFG and the propellant are clarified. Propellant modules with implanted CLPFG were fabricated. The novel grating sensor has been effectively coated and structurally packaged. Conducted experiments on strain and temperature of propellant modules. The large strain measurement of propellant from 0 µÎµ to 24000 µÎµ is realized. Solved the thorny problem of large strain measurement for propellants. In addition, the temperature discrimination measurement in the temperature range of 30 ℃ to 250 ℃ can be realized. Sensor exhibit extremely high stability characteristics and has good compatibility with propellants. The sensor implantation and extraction structure has been designed to improve the survival rate of the sensor inside the solid rocket motors (SRM). Sensors can accurately measure the mechanical and thermal state parameters of propellants, providing effective data support for the health management of SRM.

Study on the Relationship Between Diet, Physical Health and Gut Microflora of Chinese College Students.

Many elements of a modern lifestyle influence the gut microbiota but few studies have explored the effect of physical health level. This study was aimed to explore the relationship between diet, physical health and gut microbiota in Chinese college students. A total of 69 college students were recruited, including 27 college athletes (AS group) and 42 healthy controls (HC group). Fecal samples were collected for 16S rRNA sequencing. According to National Standards for Students' Physical Health (2014 revision), physical fitness measurements, dietary intake and health-related data were collected via questionnaires. ①According to the physical fitness scores, the physical fitness level of AS group was significantly higher than that of HC group (P < 0.05), there were no significant differences between the two groups in the frequency of intake of food. The frequency and duration of physical activity in the AS group were higher than those in the HC group (P < 0.05); ②The proportion and relative abundances of microorganism composition is varying at two groups: on the phylum level, AS group had mainly increased Firmicutes, Actinobacteria and reduced Bacteroidetes, Proteobacteria; on the genus level, AS group had mainly increased Faecalibacterium, Bifidobacterium and reduced Bacteroides; ③The associations with the 10 most abundant bacterial genera and physical fitness, dietary factors were investigated. Changes in the gut microbiota abundance can be sometimes reflective of a physical health status. Loss of the balance of gut microbial populations will lead to flora disorders and diseases. Therefore, further studies are needed to reveal the mechanisms behind the gut microbiota in its potential role.

Active W Sites Promoted by Defect Engineering Enhanced C2H6S3 Sensing Performance of WO3 Nanosheets.

Defect engineering has received extensive attention as an effective method to tune the gas sensing properties of semiconductor materials. Here, defective WO3 (D-WO3) nanosheets were obtained by a simple hydrogenation process with a detection limit as low as 5 ppb for dimethyl trisulfide (DMTS) and a response of 2.3 times that of the initial WO3 nanosheets to 100 ppb DMTS. Importantly, X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the partial loss of oxygen atoms in D-WO3 nanosheets, and density functional theory calculations found that the W sites near the oxygen defect showed higher adsorption energy for DMTS and transferred more electrons during the gas interaction, indicating that the active W site caused by oxygen atom loss can effectively enhance the reactivity of two-dimensional WO3 nanosheets. Different from the traditional oxygen defect model, this work reveals the positive effect of active metal sites on gas sensing for the first time, which is expected to provide an effective reference for the sensing application of defect engineering in metal oxides.

Current Status of Probiotics as Supplements in the Prevention and Treatment of Infectious Diseases.

Probiotics play an important role against infectious pathogens via their effects on the epithelium, the production of antimicrobial compounds, and competitive exclusion. Administration of probiotic supplements may reduce the risk of infectious diseases and the use of antibiotics, hence contributing to a reduction or a delay of the development of multi-resistant bacteria. Infection is a constant concern for people who experience recurrent infections, and antibiotic treatment usually fails due to antibiotic resistance. Therefore, an infection can lead to severe illness and hospitalization if left untreated. A growing number of studies have demonstrated promising results for a variety of probiotic strains used to prevent or treat acute and recurrent infectious diseases, but additional standardized clinical research is needed.

An Ultra-High-Resolution Bending Temperature Decoupled Measurement Sensor Based on a Novel Core Refractive Index-like Linear Distribution Doped Fiber.

A high-resolution and high-sensitivity fiber optic sensor based on the quasi-linear distribution of the core refractive index is designed and fabricated, which enables decouple measurement of bending and of temperature. First, single-mode fiber doped with Al2O3, Y2O3, and P2O5 was drawn through a fiber drawing tower. The fiber grating was engraved on the fiber by a femtosecond laser. Modeling analysis was conducted from quantum theory. Experimental results show that the bending sensitivity of the grating can reach 21.85 dB/m-1, which is larger than the reported sensitivity of similar sensors. In the high temperature range from room temperature to 1000 °C, the temperature sensitivity was 14.1 pm/°C. The doped grating sensor can achieve high temperature measurement without annealing, and it has a distinguished linear response from low temperature to high temperature. The bending resolution can reach 0.0004 m-1, and the temperature resolution can reach 0.007 °C. Two-parameter decoupling measurement can be realized according to the distinctive characteristic trends of the spectrum. What's more, the sensor exhibits excellent stability and a fast response time.

Exposed Mo atoms induced by micropores enhanced H2S sensing of MoO3 nanoflowers.

It is well known that the metal atoms of metal oxide semiconductor (MOS) exhibit significant activity in gas sensing. However, limited by the shielding effect of the outer oxygen atom layer, layered MoO3 is often difficult to show ideal gas adsorption activity. Hence, the MoO3 microporous nanoflowers (MPNFs) assembled by porous two-dimensional nanosheets were successfully synthesized and exhibited excellent gas sensing performance to H2S, and the response was 7.2 times higher than that of simple MoO3 nanosheets. The abundant pores of MoO3 MPNFs were due to the influence of the crystal cell shrinkage effect on the atomic arrangement, while the significantly enhanced gas sensing performance was attributed to the positive effect of the microporous structure on gas diffusion and the exposed edge Mo atoms. This was confirmed by DFT calculation results that, compared to the Mo atoms on the surface of MoO3 nanosheets, the Mo atoms around the pores were exposed because they broke through the shielding effect of the oxygen atom layer and exhibited higher adsorption activity for H2S and O2 molecules. Therefore, this work can shed a light on the design of high-performance gas sensors based on metal oxides.

Oropharyngeal Probiotic ENT-K12 Prevents Respiratory Tract Infections Among Frontline Medical Staff Fighting Against COVID-19: A Pilot Study.

Healthcare workers at the frontline are facing a substantial risk of respiratory tract infection during the COVID-19 outbreak due to an extremely stressful work schedule and public health event. A well-established first-line defense on oropharyngeal microbiome could be a promising strategy to protect individuals from respiratory tract infections including COVID-19. The most thoroughly studied oropharyngeal probiotic product which creates a stable upper respiratory tract microbiota capable of preventing upper respiratory tract infections was chosen to evaluate the safety and efficacy on reducing episodes of upper respiratory tract infections for COVID-19 healthcare workers. To our knowledge to date, this is the very first study describing the beneficial effects of oropharyngeal probiotic been administered by healthcare workers during the COVID-19 pandemic. In this randomized controlled trial, we provided the probiotics to frontline medical staff who work in the hospitals in Wuhan and had been in close contact with hospitalized COVID-19 patients for prophylactic use on a daily basis. Our finding suggests that oropharyngeal probiotic administration significantly reduced the incidence of respiratory tract infections by 64.8%, reduced the time experiencing respiratory tract infections and oral ulcer symptoms by 78%, shortened the days absent from work by 95.5%, and reduced the time under medication where there is no record of antibiotic and anti-viral drug intake in the probiotic group. Furthermore, medical staff treated with Bactoblis experienced sustained protection from respiratory tract infections since the 10th day of oropharyngeal probiotic administration resulting in an extremely low incidence rate of respiratory tract infections.

Study of the Relationship between Microbiome and Colorectal Cancer Susceptibility Using 16SrRNA Sequencing.

A lot of previous studies have recently reported that the gut microbiota influences the development of colorectal cancer (CRC) in Western countries, but the role of the gut microbiota in Chinese population must be investigated fully. The goal of this study was to determine the role of the gut microbiome in the initiation and development of CRC. We collected fecal samples of 206 Chinese individuals: 59 with polyp (group P), 54 with adenoma (group A), 51 with colorectal cancer (group CC), and 42 healthy controls (group HC).16S ribosomal RNA (rRNA) was used to compare the microbiota community structures among healthy controls, patients with polyp, and those with adenoma or colorectal cancer. Our study proved that intestinal flora, as a specific indicator, showed significant differences in its diversity and composition. Sobs, Chao, and Ace indexes of group CC were significantly lower than those of the healthy control group (CC group: Sobs, Chao, and Ace indexes were 217.3 ± 69, 4265.1 ± 80.7, and 268.6 ± 78.1, respectively; HC group: Sobs, Chao, and Ace indexes were 228.8 ± 44.4, 272.9 ± 58.6, and 271.9 ± 57.2, respectively). When compared with the healthy individuals, the species richness and diversity of intestinal flora in patients with colorectal cancer were significantly reduced: PCA and PCoA both revealed that a significant separation in bacterial community composition between the CC group and HC group (with PCA using the first two principal component scores of PC1 14.73% and PC2 10.34% of the explained variance, respectively; PCoA : PC1 = 14%, PC2 = 9%, PC3 = 6%). Wilcox tests was used to analyze differences between the two groups, it reveals that Firmicutes (P=0.000356), Fusobacteria (P=0.000001), Proteobacteria (P=0.000796), Spirochaetes (P=0.013421), Synergistetes (P=0.005642) were phyla with significantly different distributions between cases and controls. The proportion of microorganism composition is varying at different stages of colon cancer development: Bacteroidetes (52.14%) and Firmicutes (35.88%) were enriched in the healthy individuals; on the phylum level, the abundance of Bacteroidetes (52.14%-53.92%-52.46%-47.06%) and Firmicutes (35.88%-29.73%-24.27%-25.36%) is decreasing with the development of health-polyp-adenomas-CRC, and the abundance of Proteobacteria (9.33%-12.31%-16.51%-22.37%) is increasing. PCA and PCOA analysis showed there was no significant (P < 0.05) difference in species similarity between precancerous and carcinogenic states. However, the composition of the microflora in patients with precancerous lesions (including patients with adenoma and polyp) was proved to have no significant disparity (P < 0.05). Our study provides insights into new angles to dig out potential biomarkers in diagnosis and treatment of colorectal cancer and to provide scientific advice for a healthy lifestyle for the sake of gut microbiota.

Structure evolution from Prussian-blue nanocubes to hollow nanocage composites via sodium tungstate etching.

The formation path of hollow complex nanocages prepared via Na2WO4·2H2O etching, using Prussian blue as a template, is tracked, which confirms the existence of a central cross structure inside the etching products. A mechanism based on etching along edges is described. The gas sensor designed with an Fe-W hollow complex exhibits excellent performance toward CH3S3CH3.