Manipulating Electromagnetic Waves with Zero Index Materials

Zero-index material is a typical metamaterial with an effective zero refractive index, possessing a variety of exotic electromagnetic properties and particular functionalities. We have considered two kinds of zero-index materials with the first one a nearly matched zero index made of magnetic metamaterial and the second one a radially anisotropic zero index. The magnetic metamaterial-based systems are shown to be significant in wavefront engineering and flexibly tunable by an external magnetic field and a temperature field. The radially anisotropic zero-index-based systems can remarkably enhance the omnidirectional isotropic radiation by enclosing a line source and a dielectric particle within a shell configuration. The physical origin lies in that the dielectric particle effectively rescatters the trapped anisotropic higher order modes and converts them into the isotropic 0th order mode radiated outside the system. The case for the system with the loss is then examined and the energy compensation with a gain particle is also demonstrated

Towards Safe Reinforcement Learning via Constraining Conditional Value-at-Risk

Though deep reinforcement learning (DRL) has obtained substantial success, it may encounter catastrophic failures due to the intrinsic uncertainty of both transition and observation. Most of the existing methods for safe reinforcement learning can only handle transition disturbance or observation disturbance since these two kinds of disturbance affect different parts of the agent; besides, the popular worst-case return may lead to overly pessimistic policies. To address these issues, we first theoretically prove that the performance degradation under transition disturbance and observation disturbance depends on a novel metric of Value Function Range (VFR), which corresponds to the gap in the value function between the best state and the worst state. Based on the analysis, we adopt conditional value-at-risk (CVaR) as an assessment of risk and propose a novel reinforcement learning algorithm of CVaR-Proximal-Policy-Optimization (CPPO) which formalizes the risk-sensitive constrained optimization problem by keeping its CVaR under a given threshold. Experimental results show that CPPO achieves a higher cumulative reward and is more robust against both observation and transition disturbances on a series of continuous control tasks in MuJoCo

Systems engineering N-glycans of recombinant therapeutic proteins

Protein N-glycosylation reactions form a distributed reaction network spanning over different compartments of Golgi apparatus. The resulting glycan structures are influenced by glycosylation enzymes, the supply rate of nucleotide sugars, as well as competition among extending glycan substrates for a common enzyme and among different enzymes for a common substrate. Controlling the glycan profile of a therapeutic protein product is important for product quality for both innovative drugs as well as biosimilars. Metabolic engineering of the glycosylation pathway offers a venue for modulating the glycan profile. We have taken a systems engineering approach to identify, through model assisted design, the genetic manipulations that may steer the glycan flux to the desired path. However, unlike the energy metabolism pathway for which a small number of enzymes play pivotal roles in controlling the flux, the glycosylation pathway lacks key regulated steps as easily identifiable targets for genetic alteration to re-direct the flux. The model prediction thus serves only as a imprecise guide rather than a clear beacon. Furthermore, very likely multiple genetic alterations are needed in order to steer glycan flux distribution. A scheme of rapid construction of gene combinations to facilitate genetic engineering of the cell is necessary. We establish a golden gate assembly workflow for production of multi-gene constructs for engineering the glycan biosynthesis pathway. Libraries containing promoters of varying strengths, terminators, and glycosylation related coding sequences of interest, all refactored to be devoid of type IIS restriction sites, were synthesized. In the first level of assembly, an additional library of single gene constructs were formed from these base components with single reactions. In the second level of assembly, these monocistrons were then combinatorically combined to form a multi-gene cassette library. In an application of this approach, the N-glycosylation pattern of a recombinant IgG produced in CHO cells was examined with a stoichiometric network visualization tool (GlycoVis) to track the reaction paths which lead to the product glycans and identify galactosylation as potentially limiting glycan maturation. Cassettes consisting of sequences coding for nucleotide sugar synthesis enzymes, nucleotide sugar transporters, and glycosyltransferases were then selected to engineer the IgG producing cell. Multiple cassettes successfully directed the glycosylation to produce antibody with desirable glycoforms. These results served to refine our model parameters and sharpen its predictive capabilities. This combination of systems analysis and synthetic glycoengineering can be broadly applied and enhances our capability to steer N-Glycan patterns and control the quality of therapeutic proteins

4-1BB Signaling Promotes Alveolar Macrophages-Mediated Pro-Fibrotic Responses and Crystalline Silica-Induced Pulmonary Fibrosis in Mice

Silicosis is caused by exposure to crystalline silica (CS). We have previously shown that blocking 4-1BB signaling attenuated CS-induced inflammation and pulmonary fibrosis. However, the cells that express 4-1BB, which plays a vital role in promoting fibrosis, are still unknown. In this study, we demonstrated that the expression of 4-1BB is elevated in alveolar macrophages (AMs) in the lungs of CS-injured mice. CS exposure also markedly enhanced the expression of 4-1BB in macrophage-like, MH-S cells. In these cells, activation of the 4-1BB signaling with an agonist antibody led to upregulated secretion of pro-fibrotic mediators. Consistently, blocking 4-1BB downstream signaling or genetic deletion of 4-1BB alleviated pro-fibrotic responses in vitro, while treatment with a 4-1BB fusion protein promoted pro-fibrotic responses. In vivo experiments showed that blocking 4-1BB signaling decreased the expressions of pro-fibrotic mediators and fibrosis. These data suggest that 4-1BB signaling plays an important role in promoting AMs-mediated pro-fibrotic responses and pulmonary fibrosis. Our findings may provide a potential molecular target to reduce CS-induced fibrotic responses in occupational lung disease

Microwave-Assisted Synthesis of Co/CoOx Supported on Earth-Abundant Coal-Derived Carbon for Electrocatalysis of Oxygen Evolution

The evident demand for hydrogen as the ultimate energy fuel for posterity calls for the development of low-cost, efficient and stable electrocatalysts for water splitting. Herein, we report the synthesis of Co/CoOx supported on coal-derived N-doped carbon via a simple microwave-assisted method and demonstrate its application as an efficient catalyst for the oxygen evolution reaction (OER). With the optimal amount of cobalt introduced into the N-doped coal-derived, the developed catalyst achieved overpotentials of 0.370 and 0.429 V during water oxidation at current densities of 1 mA cm(-2) and 10 mA cm(-2), respectively. There was no noticeable loss in the activity of the catalyst during continuous galvanostatic polarization at a current density of 10 mA cm(-2) for a test period of 66 h. The synergistic interaction of the Co/CoOx moieties with the pyridinic and pyrollic nitrogen functional groups in the N-doped carbon, as well with the other heteroatoms species in the pristine coal favored enhancement of the OER electrocatalytic performance. (C) The Author(s) 2019. Published by ECS

A synthetic biology based cell line engineering pipeline

An ideal host cell line for deriving cell lines of high recombinant protein production should be stable, predictable, and amenable to rapid cell engineering or other forms of phenotypical manipulation. In the past few years we have employed genomic information to identify “safe harbors” for exogenous gene integration in CHO cells, deployed systems modeling and optimization to design pathways and control strategies to modify important aspects of recombinant protein productivity, and established a synthetic biology approach to implement genetic changes, all with the goal of creating a pipeline to produce “designer” cell lines. Chinese hamster ovary (CHO) cells are the preferred platform for protein production. However, the Chinese hamster genome is unstable in its ploidy, is subject to long and short deletions, duplications, and translocations. In addition, gene expression is subject to epigenetic changes including DNA methylation, histone modification and heterochromatin invasion, thus further complicating transgene expression for protein production in cell lines. With these issues in mind, we set out to engineer a CHO cell line highly amenable to stable protein production using a synthetic biology approach. We compiled karyotyping and chromosome number data of several CHO cell lines and sublines, identified genomic regions with high a frequency of gain and loss of copy number using comparative genome hybridization (CGH), and verified structural variants using sequencing data. We further used ATAC (Assay for Transposase-Accessible Chromatin) sequencing to study chromatin accessibility and epigenetic stability within the CHO genome. RNA-seq data from multiple cell lines were also used to identify regions with high transcriptional activity. Analysis of these data allowed the identification of several “safe harbor” loci that could be used for cell engineering. Based on results of the data analysis and identification of “safe harbors”, we engineered an IgG producing cell line with a single copy of the product transgene as a template cell line. This product gene site is flanked by sequences for recombinase mediated cassette exchange, therefore allowing easy substitution of the IgG producing gene for an alternative product gene. Furthermore, a “landing pad” for multi-gene cassette insertion was integrated into the genome at an additional site. Together, these sites allowed engineering of new cell lines producing a fusion protein and Erythropoietin to be generated from the template cell line. To enable rapid assembly of product transgenes and genetic elements for engineering cell attributes into multi-gene cassettes, we adopted a golden-gate based synthetic biology approach. The assembly of genetic parts into multi-gene cassettes in a LEGO-like fashion allowed different combinations of genes under the control of various promoters to be generated quickly for introduction into the template cell line. Using this engineered CHO cell line, we set out to study metabolism and product protein glycosylation for cell engineering. To guide the selection of genetic elements for cell engineering, we developed a multi-compartment kinetic model, as well as a flux model of energy metabolism and glycosylation. The transcriptome meta-data was used extensively to identify genes and isoforms expressed in the cell line and to estimate the enzyme levels in the model. The flux model was used to identify and the LEGO-like platform was used to implement the genetic changes that can alter the glycosylation pattern of the IgG produced by the template cell line. Concurrently we employed a systems optimization approach to identify the genetic alterations in the metabolic pathway to guide cell metabolism toward a favorable state. The model prediction is being implemented experimentally using the synthetic biology approach. In conclusion, we have illustrated a pipeline of rational cell line engineering that integrates genomic science, systems engineering and synthetic biology approaches. The promise, the technical challenges and possible limitations will be discussed in this presentation

Expression of plasma methylated Septin9 gene and its clinical significance in patients with gastric cancer

Background and purpose: Gastric cancer is one of the most common malignant tumors in our country. The diagnosis and treatment process of gastric cancer lacks of sensitive and specific biomarker. This study aimed to explore the expression of plasma methylated Septin9 gene (mSEPT9) and its clinical significance in patients with gastric cancer. Methods: From April 2020 to November 2020, 221 patients with gastric cancer and 34 patients with no evidence of disease who visited Zhongshan Hospital Fudan University were enrolled. The status of mSEPT9 was detected by polymerase chain reaction (PCR) fluorescence probe method, and relative mSEPT9 value was determined by the ΔΔCt method. Detailed clinical data including pathological characteristics (patients characteristics and pathology characteristics) and serum biomarkers [carcinoembryonic antigen (CEA), carbohydrate antigen (CA)12-5, CA19-9 and CA72-4] were collected and analyzed. Paired t test, χ2 test and receiver operating characteristic (ROC) curve analysis were performed for statistical analysis. Results: The positive rate, sensitivity and specificity of plasma mSEPT9 were 35%, 35% and 100%, respectively in untreated patients with gastric cancer. The positive rate of mSEPT9 was higher in patients with blood vessel invasion, serosa invasion and lymphatic metastasis, which was 46.87% vs 12.50%, 45.16% vs 14.29%, 75.00% vs 40.00%, respectively (P<0.05). The positive rate of mSEPT9 was higher in progressive disease (PD) patients than in partial response (PR) and stable disease (SD) patients, which were 68.75% and 17.74%, the differences were statistically significant (P<0.05). mSEPT9 level before PD and at the time of PD showed statistically significance. Conclusion: Plasma mSEPT9 detection demonstrates a more satisfactory diagnostic performance in gastric cancer than traditional serum biomarkers. The biomarker can provide information regarding severity with high positive rate among PD patients. The status and level of mSEPT9 were of clinical significance in evaluating tumor burden and predicting treatment response

Bridging photochemistry and photomechanics with NMR crystallography: the molecular basis for the macroscopic expansion of an anthracene ester nanorod

Crystals composed of photoreactive molecules represent a new class of photomechanical materials with the potential to generate large forces on fast timescales. An example is the photodimerization of 9-tert-butyl-anthracene ester (9TBAE) in molecular crystal nanorods that leads to an average elongation of 8%. Previous work showed that this expansion results from the formation of a metastable crystalline product. In this article, it is shown how a novel combination of ensemble oriented-crystal solid-state NMR, X-ray diffraction, and first principles computational modeling can be used to establish the absolute unit cell orientations relative to the shape change, revealing the atomic-resolution mechanism for the photomechanical response and enabling the construction of a model that predicts an elongation of 7.4%, in good agreement with the experimental value. According to this model, the nanorod expansion does not result from an overall change in the volume of the unit cell, but rather from an anisotropic rearrangement of the molecular contents. The ability to understand quantitatively how molecular-level photochemistry generates mechanical displacements allows us to predict that the expansion could be tuned from +9% to −9.5% by controlling the initial orientation of the unit cell with respect to the nanorod axis. This application of NMR-assisted crystallography provides a new tool capable of tying the atomic-level structural rearrangement of the reacting molecular species to the mechanical response of a nanostructured sample