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 <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

Celery‐derived scaffolds with liver lobule‐mimicking structures for tissue engineering transplantation

Abstract Decellularized scaffolds have a demonstrated value in liver tissue engineering. Challenges in this area are focused on effectively eliminating the biological rejection of scaffolds and finding a suitable liver cell source. Here, inspired by the natural microstructure of hepatic lobules, we present a novel decellularized celery‐derived scaffold cultured with human‐induced pluripotent stem cell‐derived hepatocytes (hiPSC‐Heps) bioengineering liver tissue construction. Because of the natural hollow channels, interconnected porous structures, and excellent physicochemical characterization of the decellularized celery‐derived scaffold, the resultant bioengineering liver tissue can maintain the hiPSC‐Heps viability and the hepatic functions in the in vitro cultures. Based on this bioengineering liver tissue, we have demonstrated its good biocompatibility and the significantly higher expressions of albumin (ALB) and periodic acid‐schiff stain (PAS) when it was implanted in nude mice. These remarkable properties endow the hiPSC‐Heps integrated decellularized celery scaffolds system with promising prospects in the field of liver transplantation and other regeneration medicine

Study on the Influence of Weld Spacing on the Tensile Strength of Laser Double-Pass Reciprocating Welding of DP780/6061-T6 Dissimilar Metals

The welding of steel–aluminum dissimilar metals plays a vital role in promoting automobile lightweight. However, it is tricky to obtain good mechanical properties of steel–aluminum laser weldments. Based on the principle of preheating welding, the laser double-pass reciprocating welding method of steel–aluminum dissimilar metals was proposed. In the experiment, different weld spacing such as 0, 0.5, 1.0, 1.5, and 2.0 mm were set, and numerical calculations of the temperature field of the molten pool were carried out. The results show that the tensile strength of weldment depends on the mechanical properties of the second weld seam in the optimal welding parameters. Compared with other weld spacing, when the weld spacing is 1.5 mm, the preheating temperature, peak temperature, and pool width on the steel side of the second weld are lower. In contrast, the weld penetration’s peak value and molten pool center’s temperature reach the maximum on the aluminum side. The thickness of the steel/aluminum transition layer changed from 14 to 11 to 8 μm with increased weld spacing. Moreover, the fracture mode of the second weld is a ductile fracture. Furthermore, the average tensile strength can reach 76.84 MPa. The results show that appropriate weld spacing and preheating temperature can effectively improve the tensile strength of the welding joint

Multidimensional landscape of non‐alcoholic fatty liver disease‐related disease spectrum uncovered by big omics data: Profiling evidence and new perspectives

Abstract Characterized by hepatic lipid accumulation, non‐alcoholic fatty liver disease (NAFLD) is a multifactorial metabolic disorder that could promote the progression of non‐alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma (HCC). Benefiting from recent advances in omics technologies, such as high‐throughput sequencing, voluminous profiling data in HCC‐integrated molecular science into clinical medicine helped clinicians with rational guidance for treatments. In this review, we conclude the majority of publicly available omics data on the NAFLD‐related disease spectrum and bring up new insights to inspire next‐generation therapeutics against this increasingly prevalent disease spectrum in the post‐genomic era

Evaluating Model-Free Reinforcement Learning toward Safety-Critical Tasks

Safety comes first in many real-world applications involving autonomous agents. Despite a large number of reinforcement learning (RL) methods focusing on safety-critical tasks, there is still a lack of high-quality evaluation of those algorithms that adheres to safety constraints at each decision step under complex and unknown dynamics. In this paper, we revisit prior work in this scope from the perspective of state-wise safe RL and categorize them as projection-based, recovery-based, and optimization-based approaches, respectively. Furthermore, we propose Unrolling Safety Layer (USL), a joint method that combines safety optimization and safety projection. This novel technique explicitly enforces hard constraints via the deep unrolling architecture and enjoys structural advantages in navigating the trade-off between reward improvement and constraint satisfaction. To facilitate further research in this area, we reproduce related algorithms in a unified pipeline and incorporate them into SafeRL-Kit, a toolkit that provides off-the-shelf interfaces and evaluation utilities for safety-critical tasks. We then perform a comparative study of the involved algorithms on six benchmarks ranging from robotic control to autonomous driving. The empirical results provide an insight into their applicability and robustness in learning zero-cost-return policies without task-dependent handcrafting. The project page is available at https://sites.google.com/view/saferlkit

Screening and validation of prognostic indicator genes in the progression of HBV related hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a rapidly progressing cancer and the main reason for cancer-related deaths. There are numerous risk factors for HCC, of which hepatitis B virus (HBV) infection is recognized as a high risk. HBV infection is accompanied by gene integration, and the liver has undergone the process of continuous and repeated damage and repair. However, predictive factors of HBV-related HCC are still limited, and the prognostic regulatory genes have not been fully elucidated. This study aims to use bioinformatics analysis to search potential prognostic genes of HBV-related HCC. Based on the full utilization of the GEO database, we screened out prognostic-related genes by performing systematic Kaplan-Meier survival analysis. The differences of the transcriptional information and protein expression were verified in the TCGA and HPA databases respectively, and the clinical characteristics of the screened genes were described by the boxplot. Five prognostic-related genes we screened, including CDK1, MAD2L1, SPP1, TYMS, and CCNA2, are strongly linked with poor prognosis in HBV-related HCC. The five prognostic-related genes have realistic clinical significance and potential as prognostic markers, and may provide new directions for basic research and clinical diagnosis

Electrodeposition of reduced graphene oxide with chitosan based on the coordination deposition method

The electrodeposition of graphene has drawn considerable attention due to its appealing applications for sensors, supercapacitors and lithium-ion batteries. However, there are still some limitations in the current electrodeposition methods for graphene. Here, we present a novel electrodeposition method for the direct deposition of reduced graphene oxide (rGO) with chitosan. In this method, a 2-hydroxypropyltrimethylammonium chloride-based chitosan-modified rGO material was prepared. This material disperses homogenously in the chitosan solution, forming a deposition solution with good dispersion stability. Subsequently, the modified rGO material was deposited on an electrode through codeposition with chitosan, based on the coordination deposition method. After electrodeposition, the homogeneous, deposited rGO/chitosan films can be generated on copper or silver electrodes or substrates. The electrodeposition method allows for the convenient and controlled creation of rGO/chitosan nanocomposite coatings and films of different shapes and thickness. It also introduces a new method of creating films, as they can be peeled completely from the electrodes. Moreover, this method allows for a rGO/chitosan film to be deposited directly onto an electrode, which can then be used for electrochemical detection