In high power fiber lasers, the degradation of beam quality caused by Raman effect has attracted more and more attention in recent years, but its physical mechanism is still unclear. We're going to ...differentiate between heat effect and nonlinear effect by duty cycle operation. The evolution of beam quality at different pump duty cycles has been studied based on a quasi-continuous wave (QCW) fiber laser. It is found that even if the Stokes intensity is only -6 dB (energy proportion: 26%) lower than that of the signal light intensity, the beam quality has no obvious change with the duty cycle of 5%; on the contrary, when the duty cycle gradually approaches 100% (CW-pumped scheme), the beam quality distortion changes faster and faster with the increase of Stokes intensity. The experimental results are contrary to core-pumped Raman effect theory IEEE Photon. Technol. Lett.34, 215 (2022)10.1109/LPT.2022.3148999, and further analysis confirms that the heat accumulation in the process of Stokes frequency shift should be responsible for this phenomenon. That is the first time, to the best of our knowledge, for intuitive reveal of the origin of stimulated Raman scattering (SRS)-induced beam quality distortion under transverse mode instability (TMI) threshold in an experiment.
In this study, Scenedesmus obliquus SJTU-3 and Chlorella pyrenoidosa SJTU-2 were cultivated with 0.03%, 5%, 10%, 20%, 30%, 50% CO2. The two microalgae could grow at 50% CO2 (>0.69gL−1) and grew well ...(>1.22gL−1) under CO2 concentrations ranging from 5% to 20%. Both of the two examined microalgae showed best growth potential at 10% CO2. The maximum biomass concentration and CO2 biofixation rate were 1.84gL−1 and 0.288gL−1d−1 for S. obliquus SJTU-3 and 1.55gL−1 and 0.260gL−1d−1 for C. pyrenoidosa SJTU-2, respectively. The main fatty acid compositions of the two examined microalgae were fatty acids with C16–C18 (>94%) under different CO2 levels. High CO2 levels (30–50%) were favorable for the accumulation of total lipids and polyunsaturated fatty acids. The present results suggested that the two microalgae be appropriate for mitigating CO2 in the flue gases and biodiesel production.
Bone marrow mesenchymal stem cells (BMSCs) have therapeutic potential in the subacute/chronic phase of acute ischemic stroke (AIS), but the underlying mechanisms are not yet fully elucidated. There ...is a knowledge gap in understanding the metabolic mechanisms of BMSCs in stroke therapy. In this study, we administered BMSCs intravenously 24 h after reperfusion in rats with transient cerebral artery occlusion (MCAO). The treatment with BMSCs for 21 days significantly reduced the modified neurological severity score of MCAO rats (P < 0.01) and increased the number of surviving neurons in both the striatum and hippocampal dentate gyrus region (P < 0.01, respectively). Moreover, BMSCs treatment resulted in significant enhancements in various structural parameters of dendrites in layer V pyramidal neurons in the injured hemispheric motor cortex, including total length (P < 0.05), number of branches (P < 0.05), number of intersections (P < 0.01), and spine density (P < 0.05). Then, we performed plasma untargeted metabolomics analysis to study the metabolic changes of BMSCs on AIS. There were 65 differential metabolites identified in the BMSCs treatment group. Metabolic profiling analysis revealed that BMSCs modulate abnormal sphingolipid metabolism and glycerophospholipid metabolism, particularly affecting core members such as sphingomyelin (SM), ceramide (Cer) and sphingosine-1-phosphate (S1P). The metabolic network analysis and pathway-based compound-reaction-enzyme-gene network analysis showed that BMSCs inhibited the Cer-induced apoptotic pathway and promoted the S1P signaling pathway. These findings suggest that the enhanced effects of BMSCs on neuronal survival and synaptic plasticity after stroke may be mediated through these pathways. In conclusion, our study provides novel insight into the potential mechanisms of BMSCs treatment in stroke and sheds light on the possible clinical translation of BMSCs.
A quantitative discussion of the combined influence of three electromechanical effects: piezoelectricity, flexoelectricity, and electrostriction in solids is provided for acoustic absorption and ...gain. While piezoelectricity occurs in non‐centrosymmetric materials only, flexoelectricity and electrostriction exist in all materials. Two important new results are demonstrated: 1) the possibility to realize acoustic gain in all materials (centrosymmetric and non‐centrosymmetric) when the acoustic Cherenkov condition is fulfilled, and 2) realization of acoustic gain in the presence of a strong dc electric field, even when the Cherenkov condition is not fulfilled, in the case of strong cross‐coupling between piezoelectricity, flexoelectricity, and electrostriction. A simple analytical expression for the acoustic dispersion relation is derived for the combined effect of piezoelectricity, flexoelectricity, and electrostriction. At lower frequencies, the piezoelectric effect dominates for inversion‐asymmetric materials. At high frequencies (≈>1 MHz) flexoelectricity becomes increasingly important and eventually provides a major mechanism for gain and absorption in barium titanate (BaTiO3). In the presence of strong electric fields (≈>1 MV m−1), electrostriction provides a dominant isolated contribution to absorption/gain in BaTiO3. Strong coupling between the three electromechanical contributions determines the total absorption/gain coefficient.
Plot of the imaginary wave vector component k1″ vs electric field E0 and acoustic frequency ω/(2π). Loss and gain regimes are indicated.
Rice straw hydrolysate was used as lignocellulose-based carbon source for Chlorella pyrenoidosa cultivation and the feasibility of in situ biodiesel production was investigated. 13.7 g/L sugar was ...obtained by enzymatic hydrolyzation of rice straw. Chlorella pyrenoidosa showed a rapid growth in the rice straw hydrolysate medium, the maximum biomass concentration of 2.83 g/L was obtained in only 48 hours. The lipid content of the cells reached as high as 56.3%. In situ transesterification was performed for biodiesel production. The optimized condition was 1 g algal powder, 6 mL n-hexane, and 4 mL methanol with 0.5 M sulfuric acid at the temperature of 90°C in 2-hour reaction time, under which over 99% methyl ester content and about 95% biodiesel yield were obtained. The results suggested that the method has great potential in the production of biofuels with lignocellulose as an alternative carbon source for microalgae cultivation.
Three new graphitic C3N4 allotropes are identified in stochastic group and graph constrained searches and systematically investigated by first-principles calculations. They are named as √13-C3N4, ...√16-C3N4 and √21-C3N4 according to their structure features that can be constructed through introducing atomic defects in √13-, √16- and √21- super cells of a hypothetical hexagonal carbon nitride structure, respectively. These three new C3N4 allotropes are structurally quite similar to the widely investigated graphitic C3N4 structures based on triazine (√4-C3N4) and heptazine (√9-C3N4). The calculated total energies of √13-C3N4, √16-C3N4 and √21-C3N4 are 55 meV/atom, 12 meV/atom and 47 meV/atom higher than that of the ground state √9-C3N4, which indicate that they are energetically stable. They are also confirmed to be thermo-stable phases at 300 K temperature condition through ab initio molecular dynamics (MD) simulations. The HSE06 based calculations show that √13-C3N4, √16-C3N4 and √21-C3N4 are semiconductors with indirect band gaps of 1.921 eV, 2.056 eV and 2.808 eV, respectively. Their band gaps and band edge positions are proper for sun-light driven water splitting. The √21-C3N4 with remarkable stability and proper electronic properties, comparable to the widely used √9-C3N4, for sun-light-driven water splitting at both acidic and neutral environments is highly expected to be synthesized in future experiment for application in sun-light-driven water splitting.
•Three new 2D graphitic C3N4 allotropes are theoretically predicted.•These three 2D graphitic C3N4 allotropes possess remarkable energetic stabilities.•These three 2D graphitic C3N4 allotropes are potential materials for sun-light-driven water splitting.
Background Some cohort studies have explored the effects and safety of polymyxin B (PMB) in comparison to other antibiotics for the treatment of nosocomial infections, yielding inconsistent results. ...This systematic review aims to explore the effectiveness and safety of PMB and compared it with other antibiotics. Methods A systematic literature search was conducted in PubMed, Embase, the Cochrane Library, and Web of Science, searching specific terms to identify quantitative cohort studies or RCTs that compared the effects of PMB with other antibiotics in terms of their efficacy and safety. The Newcastle–Ottawa Scale (NOS) was conducted to evaluate the risk of bias of observational studies. Odds ratios with 95% confidence intervals were used for outcome assessment. We evaluated heterogeneity using the I 2 test. Results A total of 22 observational trials were included in the analysis. The PMB group had a higher mortality rate compared to the control group (odds ratio: 1.84, 95% CI: 1.36–2.50, p <0.00001, I 2 = 73%). while, the ceftazidime-avibactam group demonstrated a distinct advantage with lower mortality rates, despite still exhibiting high heterogeneity (odds ratio 2.73, 95% confidence interval 1.59–4.69; p = 0.0003; I 2 = 53%). Additionally, the PMB group had a lower nephrotoxicity rate compared to the colistin group but exhibited high heterogeneity in the results (odds ratio 0.58, 95% CI 0.36–0.93; p = 0.02; I 2 = 73%). Conclusion In patients with nosocomial infections, PMB is not superior to other antibiotics in terms of mortality, specifically when compared to ceftazidime-avibactam. However, PMB demonstrated an advantage in terms of nephrotoxicity compared to colistin.
BEKG: A built environment knowledge graph Yang, Xiaojun; Zhong, Haoyu; Wang, Zhengdong ...
Building research and information : the international journal of research, development and demonstration,
02/2024, Letnik:
52, Številka:
1-2
Journal Article
Recenzirano
Odprti dostop
In recent years, the digitalization of the built environment has progressed rapidly due to the development of modern design and construction technologies. However, the need for extensive professional ...knowledge in this field has not been met by practitioners and scholars. To address this problem, a study was conducted to build a knowledge graph in the built environment domain, which stores entities and their connections in a graph data model. To achieve it, this research collected more than 80,000 paper abstracts from the built environment domain. To ensure the accuracy of entities and relationships in the knowledge graph, two well-annotated datasets were created with 29 types of relationships, each containing 2000 and 1450 instances, respectively, for Named Entity Recognition (NER) and relationship extraction (RE) tasks. Two BERT-based models were trained on these datasets and achieved over 85% accuracy in both tasks. Using these models, over 200,000 high-quality relationships and entities were extracted from abstract data. This comprehensive knowledge graph will help practitioners and scholars better understand the built environment domain.
Morphological profiles (MPs) have been proposed for the segmentation and classification of high spatial resolution (HSR) images. A shortcoming of the originally proposed MPs is that the profiles were ...only based on structuring elements (SEs) of one particular shape, suggesting that such MPs may not be suitable for detecting different shapes in images. To better fit several shapes in a given image, a new approach based on mathematical morphology is proposed to extract structural information from HSR images and consequently yield new versions of MPs. The classification results for the new MPs are compared with the classification of spatial features extracted with the use of pixel shape index, gray level co-occurrence matrix, and previously proposed MPs. The experimental results suggest the following: 1) structural and spectral features can complement each other and their integration can improve classification accuracy and 2) MPs constructed by differently shaped SEs are less sensitive to salt-and-pepper noise than those constructed by fixed-shaped SEs.
Computed tomography (CT) examination is the major measure for detecting and diagnosis of foreign bodies in human body. Although CT has high sensitivity in diagnosis of foreign body, some interference ...factors may still lead to missed diagnosis or misdiagnosis. Here we report a rare case that a bamboo stick accidentally pierced into the left chest of a young man who was drunk and unware of this hurt. The patient experienced cough, chest pain, fever, hemoptysis, and was misdiagnosed as primary and secondary tuberculosis based on chest CT examinations at a local hospital, although no tubercular bacillus detected by sputum smear. He subsequently received anti-tuberculous treatments in the following three years, but no improvement of his symptoms was observed. Until one month before his death, the bamboo stick was detected by spiral CT examination as well as three-dimensional image reconstruction at another hospital. Postmortem examination revealed pneumonia, pulmonary infarction, and abscess as the causes of his death. We analyze the potential reasons of misdiagnosis in this case, aiming to provide reference for the diagnosis and treatment of pulmonary inflammation associated with foreign body in the future.
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