Fundamental Investigation on Polishing of Internal Structures Made by Laser-based Powder Bed Fusion

This study aims at utilizing a self-developed hybrid polishing system to establish polishing capabilities of electropolishing (EP), abrasive fluid polishing (AFP), multiple polishing in different sequences and innovative hybrid polishing for the internal structures prepared by laser-based powder bed fusion (L-PBF). By studying polishing effects on various inner surfaces, the relationships between polishing processes and material removal mechanisms of L-PBF surface features are established considering microstructural differences of surface features. The thesis starts with a comprehensive introduction of the project and then a literature review outlining L-PBF process, application of typical L-PBF internal structures, surface characteristics, advantages and limitations of current polishing methods for L-PBF inner surfaces. Breakthroughs in the surface finish of L-PBF internal structures are required in order to improve surface quality to meet the specific requirements of product performance. It is notified that EP and AFP exhibit complementary advantages in the polishing of internal structures among various polishing technologies. In the chapter 3, different types of inner surfaces for fundamental investigation and typical internal structures for application development are designed, and prepared by L-PBF using 316L stainless steel and Ti6Al4V powders. Then, un-sintered powders and sintered area are characterized as common surface features on L-PBF top, face up, side and face down surfaces considering the differences of morphology and microstructure. Meanwhile, an innovative hybrid polishing system which could carry out EP, AFP, their multiple polishing and hybrid polishing is established for the surface improvement of the L-PBF inner surfaces and internal structures. In the chapter 4, a polishing mode consisting of two-step EP is developed by using different potentials and polishing time for L-PBF 316L stainless steel and Ti6Al4V inner surfaces after parametric study in the developed polishing system. Based on material removal characteristics of surface features, the effectiveness and high efficiency of the two-step EP are demonstrated. Considering polishing characteristics of AFP, the inlet design of polishing chamber is improved and the material removal process of various L-PBF internal surfaces are discussed by analyzing the evolution of surface morphology, roughness and microstructure on cross sections in the chapter 5. In the chapter 6, multiple polishing in different sequences and hybrid polishing based on EP and AFP are investigated for L-PBF inner surfaces. It is found that L-PBF inner surfaces after single polishing can be further improved by multiple polishing in different sequences because of the complementary characteristics of EP and AFP in removing L-PBF surface features. In addition, hybrid polishing can perform EP and AFP simultaneously without interfering with each other, showing great potential in improving polishing efficiency of L-PBF inner surfaces. In the chapter 7, different polishing processes are applied to three typical L-PBF internal structures. The superiority of multiple polishing in different sequences and hybrid polishing for L-PBF inner structures is verified. Overall, it is confirmed that the self-developed innovative hybrid polishing system is capable of polishing various L-PBF internal structures with reliable results. Fundamental research on material removal characteristics of L-PBF surface features during polishing provides a theoretical basis for the applications of multiple and hybrid polishing based on EP and AFP. High efficiency and cost- effectiveness make the hybrid polishing system a strong candidate for industrial implementation in the surface finish of L-PBF internal structures

Shape Anchor Guided Holistic Indoor Scene Understanding

This paper proposes a shape anchor guided learning strategy (AncLearn) for robust holistic indoor scene understanding. We observe that the search space constructed by current methods for proposal feature grouping and instance point sampling often introduces massive noise to instance detection and mesh reconstruction. Accordingly, we develop AncLearn to generate anchors that dynamically fit instance surfaces to (i) unmix noise and target-related features for offering reliable proposals at the detection stage, and (ii) reduce outliers in object point sampling for directly providing well-structured geometry priors without segmentation during reconstruction. We embed AncLearn into a reconstruction-from-detection learning system (AncRec) to generate high-quality semantic scene models in a purely instance-oriented manner. Experiments conducted on the challenging ScanNetv2 dataset demonstrate that our shape anchor-based method consistently achieves state-of-the-art performance in terms of 3D object detection, layout estimation, and shape reconstruction. The code will be available at https://github.com/Geo-Tell/AncRec

Effect of Frying Conditions on Acrylamide and 5-Hydroxymethylfurfural Formation in French Fries

In this study, the relationship between the formation of acrylamide (AA) and that of 5-hydroxymethylfurfural (5-HMF), as well as the correlation with the content of α-dicarbonyl compounds as intermediate products in French fries were studied using Pearson correlation analysis and principal component analysis (PCA), and the correlation between the formation of AA and 5-HMF and the sensory score, color, water content and oil absorption of French fries was also discussed. The results showed that with an increase in frying time or temperature, the contents of AA, 5-HMF and α-dicarbonyl compounds in French fries increased significantly, water content decreased, and oil absorption increased gradually. In addition, lightness (L* value) and yellowness (b* value) tended to decrease, while redness (a* value) tended to increase. There was a significantly positive correlation between AA and 5-HMF contents under the different conditions tested. Moreover, AA and 5-HMF contents showed a significantly positive correlation with the content of α-dicarbonyl compounds and oil absorption, but a significantly negative correlation with water content, L* value and b* value. AA content was positively correlated with a* value. It was found that the results of the PCA model were consistent with the linear curves of the contents of AA, 5-HMF and α-dicarbonyl compounds versus frying temperature and time. Frying for 5 min at 170 ℃ not only ensured the best sensory quality of French fries, but also helped to reduce the formation of hazardous substances

Catalytic Mechanism Investigation of Lysine-Specific Demethylase 1 (LSD1): A Computational Study

Lysine-specific demethylase 1 (LSD1), the first identified histone demethylase, is a flavin-dependent amine oxidase which specifically demethylates mono- or dimethylated H3K4 and H3K9 via a redox process. It participates in a broad spectrum of biological processes and is of high importance in cell proliferation, adipogenesis, spermatogenesis, chromosome segregation and embryonic development. To date, as a potential drug target for discovering anti-tumor drugs, the medical significance of LSD1 has been greatly appreciated. However, the catalytic mechanism for the rate-limiting reductive half-reaction in demethylation remains controversial. By employing a combined computational approach including molecular modeling, molecular dynamics (MD) simulations and quantum mechanics/molecular mechanics (QM/MM) calculations, the catalytic mechanism of dimethylated H3K4 demethylation by LSD1 was characterized in details. The three-dimensional (3D) model of the complex was composed of LSD1, CoREST, and histone substrate. A 30-ns MD simulation of the model highlights the pivotal role of the conserved Tyr761 and lysine-water-flavin motif in properly orienting flavin adenine dinucleotide (FAD) with respect to substrate. The synergy of the two factors effectively stabilizes the catalytic environment and facilitated the demethylation reaction. On the basis of the reasonable consistence between simulation results and available mutagenesis data, QM/MM strategy was further employed to probe the catalytic mechanism of the reductive half-reaction in demethylation. The characteristics of the demethylation pathway determined by the potential energy surface and charge distribution analysis indicates that this reaction belongs to the direct hydride transfer mechanism. Our study provides insights into the LSD1 mechanism of reductive half-reaction in demethylation and has important implications for the discovery of regulators against LSD1 enzymes

Pilot Study on Image Quality and Radiation Dose of CT Colonography with Adaptive Iterative Dose Reduction Three-Dimensional

Objective: To investigate image quality and radiation dose of CT colonography (CTC) with adaptive iterative dose reduction three-dimensional (AIDR3D). Methods: Ten segments of porcine colon phantom were collected, and 30 pedunculate polyps with diameters ranging from 1 to 15 mm were simulated on each segment. Image data were acquired with tube voltage of 120 kVp, and current doses of 10 mAs, 20 mAs, 30 mAs, 40 mAs, 50 mAs, respectively. CTC images were reconstructed using filtered back projection (FBP) and AIDR3D. Two radiologists blindly evaluated image quality. Quantitative evaluation of image quality included image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Qualitative image quality was evaluated with a five-score scale. Radiation dose was calculated based on dose-length product. Ten volunteers were examined supine 50 mAs with FBP and prone 20 mAs with AIDR3D, and image qualities were assessed. Paired t test was performed for statistical analysis. Results: For 20 mAs with AIDR3D and 50 mAs with FBP, image noise, SNRs and CNRs were (16.4 ± 1.6) HU vs. (16.8 ± 2.6) HU, 1.9 ± 0.2 vs. 1.9 ± 0.4, and 62.3 ± 6.8 vs. 62.0 ± 6.2, respectively; qualitative image quality scores were 4.1 and 4.3, respectively; their differences were all not statistically significant. Compared with 50 mAs with FBP, radiation dose (1.62 mSv) of 20 mAs with AIDR3D was decreased by 60.0%. There was no statistically significant difference in image noise, SNRs, CNRs and qualitative image quality scores between prone 20 mAs with AIDR3D and supine 50 mAs with FBP in 10 volunteers, the former reduced radiation dose by 61.1%. Conclusion: Image quality of CTC using 20 mAs with AIDR3D could be comparable to standard 50 mAs with FBP, radiation dose of the former reduced by about 60.0% and was only 1.62 mSv

Plant biomass allocation and driving factors of grassland revegetation in a Qinghai-Tibetan Plateau chronosequence

Biomass allocation is a key factor in understanding how ecosystems respond to changing environmental conditions. The role of soil chemistry in the above- and belowground plant biomass allocation in restoring grassland is still incompletely characterized. Consequently, it has led to two competing hypotheses for biomass allocation: optimal partitioning, where the plants allocate biomass preferentially to optimize resource use; and the isometric hypothesis, which postulates that biomass allocation between roots and shoots is fixed. Here we tested these hypotheses over a chronosequence of alpine grasslandsion undergoing restoration in the Qinghai-Tibetan Plateau, these range from severely degraded to those with 18 years of revegetation with an intact grassland (as a reference). A high proportion of biomass was allocated to the roots in the revegetated grasslands, and more biomass to shoots in the degraded and intact grasslands. The grasslands gradually decreased their root to shoot ratio as revegetation continued, with the lowest value in year 18 of revegetation. Our results showed that aboveground biomass (AGB) was increased by available phosphorus (P), soil moisture, and negatively related to bulk density, while belowground biomass (BGB) was positively impacted by total P and negatively by nitrate nitrogen (N). The trade-off between them was positively associated with available P and nitrate-N, and soil nutrient availability is more linked to increased AGB relative to BGB. Our study indicates that biomass allocation is highly variable during the revegetation period from degraded grassland, and is linked with soil properties, thus supporting the optimal partitioning hypothesis.</p

C5aR1 shapes a non-inflammatory tumor microenvironment and mediates immune evasion in gastric cancer

C5a receptor 1 (C5aR1) is associated with various inflammatory processes, the pathogenesis of immune diseases, and tumor growth. However, its role in the tumor microenvironment of gastric cancer (GC) remains unclear. In this study, the expression of C5aR1 in GC and normal gastric mucosa tissues was compared using data retrieved from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases, and the results were validated by in vitro qRT-PCR and immunohistochemical analyses. The relationship between C5aR1 expression and the overall survival of patients with GC was analyzed using the Kaplan–Meier method. Subsequently, enrichment analysis was performed, and the signaling pathways were screened. C5aR1 expression was also correlated with genes related to the immune checkpoint and immune cell infiltration. The results revealed that C5aR1 expression was enhanced in GC tissues compared to normal gastric tissues, and that patients with high expression of C5aR1 had a worse 10-year overall survival compared to those showing low expression of C5aR1. Functional analysis revealed that C5aR1 is a gene related to theimmune system and may play a crucial role in inflammatory and tumor immune responses. Additionally, C5aR1 showed a positive correlation with most immune checkpoint-related genes and a negative correlation with natural killer cells, dendritic cells, and CD8+ T cells. Immune evasion risk was observed to be significantly greater in patients with higher expression of C5aR1 than in those with lower expression. The results of this study reveal that C5aR1 shapes a non-inflammatory tumor microenvironment in GC and mediates immune evasion

Molecular Basis of NDM-1, a New Antibiotic Resistance Determinant

The New Delhi Metallo-β-lactamase (NDM-1) was first reported in 2009 in a Swedish patient. A recent study reported that Klebsiella pneumonia NDM-1 positive strain or Escherichia coli NDM-1 positive strain was highly resistant to all antibiotics tested except tigecycline and colistin. These can no longer be relied on to treat infections and therefore, NDM-1 now becomes potentially a major global health threat

(+)-Rutamarin as a Dual Inducer of Both GLUT4 Translocation and Expression Efficiently Ameliorates Glucose Homeostasis in Insulin-Resistant Mice

Glucose transporter 4 (GLUT4) is a principal glucose transporter in response to insulin, and impaired translocation or decreased expression of GLUT4 is believed to be one of the major pathological features of type 2 diabetes mellitus (T2DM). Therefore, induction of GLUT4 translocation or/and expression is a promising strategy for anti-T2DM drug discovery. Here we report that the natural product (+)-Rutamarin (Rut) functions as an efficient dual inducer on both insulin-induced GLUT4 translocation and expression. Rut-treated 3T3-L1 adipocytes exhibit efficiently enhanced insulin-induced glucose uptake, while diet-induced obese (DIO) mice based assays further confirm the Rut-induced improvement of glucose homeostasis and insulin sensitivity in vivo. Subsequent investigation of Rut acting targets indicates that as a specific protein tyrosine phosphatase 1B (PTP1B) inhibitor Rut induces basal GLUT4 translocation to some extent and largely enhances insulin-induced GLUT4 translocation through PI3 kinase-AKT/PKB pathway, while as an agonist of retinoid X receptor α (RXRα), Rut potently increases GLUT4 expression. Furthermore, by using molecular modeling and crystallographic approaches, the possible binding modes of Rut to these two targets have been also determined at atomic levels. All our results have thus highlighted the potential of Rut as both a valuable lead compound for anti-T2DM drug discovery and a promising chemical probe for GLUT4 associated pathways exploration

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data