Chem & Bio Engineering最新文献

{"title":"Non-monotonic Information and Shape Evolution of Polymers Enabled by Spatially Programmed Crystallization and Melting","authors":"Xing Zhang,&nbsp;Yichen Zhou,&nbsp;Mengzhe Han,&nbsp;Ying Zheng,&nbsp;Junfeng Liu,&nbsp;Yongzhong Bao,&nbsp;Guorong Shan,&nbsp;Chengtao Yu* and Pengju Pan*,&nbsp;","doi":"10.1021/cbe.4c0005810.1021/cbe.4c00058","DOIUrl":"https://doi.org/10.1021/cbe.4c00058https://doi.org/10.1021/cbe.4c00058","url":null,"abstract":"<p >Stimuli-responsive polymer materials are a kind of intelligent material which can sense and respond to external stimuli. However, most current stimuli-responsive polymers only exhibit a monotonic response to a single constant stimulus but cannot achieve dynamic evolution. Herein, we report a method to achieve a non-monotonic response under a single stimulus by regionalizing the crystallization and melting kinetics in semicrystalline polymers. Based on the influence of cross-linking on the crystallization and melting kinetics of polymers, we employ light to spatially regulate the cross-linking degree in polymers. The prepared material can realize the self-evolved encryption of pattern information and the non-monotonic shape evolution without complex multiple stimuli. By combination of pattern and shape evolution, the coupled encryption of shape and pattern can be achieved. This approach empowers polymers with the ability to evolve under constant stimulus, offering insights into the functional design of polymer materials.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 9","pages":"790–797 790–797"},"PeriodicalIF":0.0,"publicationDate":"2024-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/cbe.4c00058","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142517117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhancing Substrate Preference of Iridoid Synthase via Focused Polarity-Steric Mutagenesis Scanning","authors":"Huifen Yu,&nbsp;Cuifang Ye,&nbsp;Yong Wang,&nbsp;Zhe Wang,&nbsp;Sai Fang,&nbsp;Huanhuan Jin,&nbsp;Lirong Yang,&nbsp;Wenlong Zheng* and Jianping Wu*,&nbsp;","doi":"10.1021/cbe.4c0001210.1021/cbe.4c00012","DOIUrl":"https://doi.org/10.1021/cbe.4c00012https://doi.org/10.1021/cbe.4c00012","url":null,"abstract":"<p >Nepetalactol serves as the scaffold for most iridoids, which exhibit a wide range of biological and pharmacological activities. Iridoid synthase (ISY) plays a crucial role in the <i>in vivo</i> synthesis of nepetalactol from 8-oxogeranial. However, the substrate promiscuity of ISY could result in a deviation of flux toward off-target routes. In this work, the substrate preference (SP, the ratio of activity for 8-oxogeranial to geranial) of ISY for nepetalactol was improved by directed evolution. First, the strategy of focused polarity-steric mutagenesis scanning (FPSMS) was performed to construct a small mutant library with <i>Nm</i>ISY2 from <i>Nepeta mussinii</i> as an object. Four amino acid residues with varying polarity and steric hindrance, including alanine, aspartic acid, serine, and arginine, were incorporated to scan hot spots. Consequently, four sites of W109, M217, K343, and W345 with a significant impact on the substrate preference of <i>Nm</i>ISY2 were found. Then, the four sites were combined by a combinatorial active-site saturation test/iterative saturation mutagenesis (CAST/ISM) strategy. As a result, the mutant W345D/K343M/W109Y (3M+) was obtained with a significantly increased SP value for <b>6</b> from 8.5 to 293.1. Molecular dynamics simulations revealed that the steric hindrance and polarity of the substrate tunnel played pivotal roles in the SP value of <i>Nm</i>ISY2. Notably, upon integration of 3M+ into <i>Pichia pastoris</i>, the <i>de novo</i> titer of <b>6</b> increased by 24.9 times, reaching 15.8 mg/L. This study offers a strategic approach to improving the substrate preference of enzymes.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 10","pages":"826–835 826–835"},"PeriodicalIF":0.0,"publicationDate":"2024-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/cbe.4c00012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142736463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering Mechanisms of CO2-Selective Recognition over Acetylene within Porous Materials","authors":"Zhaoqiang Zhang,&nbsp; and ,&nbsp;Dan Zhao*,&nbsp;","doi":"10.1021/cbe.4c00035","DOIUrl":"10.1021/cbe.4c00035","url":null,"abstract":"<p >Reverse adsorption of carbon dioxide (CO₂) from acetylene (C₂H₂) presents both significant importance and formidable challenges, particularly in the context of carbon capture, energy efficiency, and environmental sustainability. In this Review, we delve into the burgeoning field of reverse CO₂/C₂H₂ adsorption and separation, underscoring the absence of a cohesive materials design strategy and a comprehensive understanding of the CO₂-selective capture mechanisms from C₂H₂, in contrast to the quite mature methodologies available for C₂H₂-selective adsorption. Focusing on porous materials, the latest advancements in CO₂-selective recognition mechanisms are highlighted. The review establishes that the efficacy of CO₂ recognition from C₂H₂ relies intricately on a myriad of factors, including pore architecture, framework flexibility, functional group interactions, and dynamic responsive behaviors under operating conditions. It is noted that achieving selectivity extends beyond physical sieving, necessitating meticulous adjustments in pore chemistry to exploit the subtle differences between CO₂ and C₂H₂. This comprehensive overview seeks to enhance the understanding of CO₂-selective recognition mechanisms, integrating essential insights crucial for the advancement of future materials. It also lays the groundwork for innovative porous materials in CO₂/C₂H₂ separation, addressing the pressing demand for more efficient molecular recognition within gas separation technologies.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 5","pages":"366–380"},"PeriodicalIF":0.0,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/cbe.4c00035","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140985598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Harnessing Solar-Salinity Synergy with Porphyrin-Based Ionic Covalent-Organic-Framework Membranes for Enhanced Ionic Power Generation","authors":"Weipeng Xian,&nbsp;Changjia Zhu,&nbsp;Zhuozhi Lai,&nbsp;Qing Guo,&nbsp;Di Wu,&nbsp;Qing-Wei Meng,&nbsp;Sai Wang,&nbsp;Shengqian Ma and Qi Sun*,&nbsp;","doi":"10.1021/cbe.3c00119","DOIUrl":"10.1021/cbe.3c00119","url":null,"abstract":"<p >Nature seamlessly integrates multiple functions for energy conversion, utilizing solar energy and salinity gradients as the primary drivers for ionic power generation. The creation of artificial membranes capable of finely controlling ion diffusion within nanoscale channels, driven by diverse forces, remains a challenging endeavor. In this study, we present an innovative approach: an ionic covalent-organic framework (COF) membrane constructed using chromophoric porphyrin units. The incorporation of ionic groups within these nanoconfined channels imparts the membrane with exceptional charge screening capabilities. Moreover, the membrane exhibits photoelectric responsivity, enhancing the ion conductivity upon exposure to light. As a result, this leads to a substantial increase in the output power density. In practical terms, when subjected to a salinity gradient of 0.5/0.01 M NaCl and exposed to light, the device achieved an outstanding peak power density of 18.0 ± 0.9 W m^–2, surpassing the commercial benchmark by 3.6-fold. This innovative membrane design not only represents a significant leap forward in materials science but also opens promising avenues for advancing sustainable energy technologies.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 5","pages":"461–468"},"PeriodicalIF":0.0,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/cbe.3c00119","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140999250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photoreaction Drives Efficient, Precise, and Sustainable Additive Manufacturing","authors":"Jinghan Hu,&nbsp;Dan Wang and Haiyan Peng*,&nbsp;","doi":"10.1021/cbe.3c00126","DOIUrl":"10.1021/cbe.3c00126","url":null,"abstract":"<p >Additive manufacturing, normally referred to as three-dimensional (3D) printing, has been maturing rapidly in recent years and widely utilized in various industrial fields, because it can create predesigned functional products with sophisticated structures that are basically difficult to achieve using traditional methods. Among all 3D printing technologies, vat photopolymerization has attracted much attention because of its outstanding advantages such as fast printing speed, high precision, and ease of formulating. In recent years, many breakthroughs in photopolymerization based 3D printing have been achieved by photoreaction design regarding photopolymerizable monomers, photoinitiating systems, inhibition functions, light sourcs, etc., but challenges remain. This Perspective attempts to highlight these great advances regarding the promotion of printing efficiency, accuracy, and sustainability. At the end, several challenges, such as longer-wavelength printing, printing of functional materials, and multimaterial printing, are discussed, which must be carefully addressed to meet the increasing requirements of future high-performance additive manufacturing.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 5","pages":"414–426"},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/cbe.3c00126","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141007953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Usefulness of Lumped Kinetic Modeling.","authors":"Sebastian-Mark Lorbach, Andreas Erwin Lechleitner, Fabian Zapf, Markus Lehner","doi":"10.1021/cbe.4c00032","DOIUrl":"10.1021/cbe.4c00032","url":null,"abstract":"<p><p>Chemical recycling of plastic wastes through pyrolysis, gasification, or partial oxidation is a promising alternative to landfill disposal and incineration which must be applied in a future circular economy. These technologies enable the chemical industry, which currently heavily relies on crude oil, to obtain necessary chemical feedstock from postconsumer plastic waste. Kinetic models of pyrolysis and gasification reactions are required to dimension and design these processes on an industrial scale. The creation of detailed kinetic networks is often not feasible due to their complexity in this application, which is when the lumped kinetic modeling approach is used. This work develops and compares five lumped kinetic models for the co-pyrolysis of LDPE with a heavy petroleum fraction in a tubular reactor. A priori lumping is used for four models, and the fifth is created using a posteriori principle whereby in each model the product mixture is defined by eight lumps distinguished by their boiling point. The aim of this work is to compare different approaches for modeling reaction pathways in lumped kinetic models and to identify their impact on the predictive accuracy of the model. It was shown that all of the modeling approaches and the resulting models have similar prediction accuracies and deviations but with different kinetic parameters. Each model was used for a scale-up of an industrial-sized reactor to check whether the model had an influence on the design or predicted operation of the reactor.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 7","pages":"623-632"},"PeriodicalIF":0.0,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11835281/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143461353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Usefulness of Lumped Kinetic Modeling","authors":"Sebastian-Mark Lorbach*,&nbsp;Andreas Erwin Lechleitner,&nbsp;Fabian Zapf and Markus Lehner,&nbsp;","doi":"10.1021/cbe.4c0003210.1021/cbe.4c00032","DOIUrl":"https://doi.org/10.1021/cbe.4c00032https://doi.org/10.1021/cbe.4c00032","url":null,"abstract":"<p >Chemical recycling of plastic wastes through pyrolysis, gasification, or partial oxidation is a promising alternative to landfill disposal and incineration which must be applied in a future circular economy. These technologies enable the chemical industry, which currently heavily relies on crude oil, to obtain necessary chemical feedstock from postconsumer plastic waste. Kinetic models of pyrolysis and gasification reactions are required to dimension and design these processes on an industrial scale. The creation of detailed kinetic networks is often not feasible due to their complexity in this application, which is when the lumped kinetic modeling approach is used. This work develops and compares five lumped kinetic models for the co-pyrolysis of LDPE with a heavy petroleum fraction in a tubular reactor. A priori lumping is used for four models, and the fifth is created using a posteriori principle whereby in each model the product mixture is defined by eight lumps distinguished by their boiling point. The aim of this work is to compare different approaches for modeling reaction pathways in lumped kinetic models and to identify their impact on the predictive accuracy of the model. It was shown that all of the modeling approaches and the resulting models have similar prediction accuracies and deviations but with different kinetic parameters. Each model was used for a scale-up of an industrial-sized reactor to check whether the model had an influence on the design or predicted operation of the reactor.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 7","pages":"623–632 623–632"},"PeriodicalIF":0.0,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/cbe.4c00032","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142020154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of Shaped MIL-100(Fe) Granules for High-Performing Adsorption Desalination: From Formulation Optimization to System Test","authors":"Hao Chen,&nbsp;Qiancan Wang,&nbsp;Long Chen,&nbsp;Shanshan Cai,&nbsp;Jing Lei and Song Li*,&nbsp;","doi":"10.1021/cbe.4c0000810.1021/cbe.4c00008","DOIUrl":"https://doi.org/10.1021/cbe.4c00008https://doi.org/10.1021/cbe.4c00008","url":null,"abstract":"<p >Adsorption desalination (AD) driven by low-grade renewable energy or waste heat is a sustainable solution to the water crisis. Recently, metal–organic frameworks (MOFs) with excellent water adsorption performances have been recognized as some of the most promising candidates for AD. However, previous studies mainly focused on MOFs in powder form, causing pipe clogging and a drastic pressure drop, which inspire the development of shaped MOFs for industrial use. In this work, MIL-100(Fe) with high water stability, high adsorption capacity, and mild synthesis conditions was chosen, and the optimal formulation of the shaped MIL-100(Fe) granules using different binders was explored. The high-performing MIL-100(Fe)@5PVB granule containing 5% polyvinyl butyral (PVB) with outstanding adsorption performance and mechanical strength was selected and massively prepared for AD system testing. It is found that, although binder content decreased the surface area, pore volume, and water uptake of MIL-100(Fe), the mechanical strength and adsorption kinetics of shaped MIL-100(Fe)@5PVB were enhanced, which favor its performance in an AD system. Moreover, system testing demonstrated that the desalination performance of the AD system based on the adsorption beds of MIL-100(Fe)@5PVB outperformed both silica gel and MIL-100(Fe) powder. The specific daily water production (SDWP) of the AD system based on MIL-100(Fe)@5PVB (28.74 m³/ton/day) is 30% higher than that based on MIL-100(Fe) powder (19 m³/ton/day). Such a phenomenon is mainly contributed by the improved water adsorption dynamics of MIL-100(Fe)@5PVB granules that favors the mass transfer efficiency in the adsorption bed. This work opens up the possibility for the development of high-performing shaped MOFs for adsorption desalination from the perspectives of formulation optimization and system testing.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 10","pages":"817–825 817–825"},"PeriodicalIF":0.0,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/cbe.4c00008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142736459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of Shaped MIL-100(Fe) Granules for High-Performing Adsorption Desalination: From Formulation Optimization to System Test.","authors":"Hao Chen, Qiancan Wang, Long Chen, Shanshan Cai, Jing Lei, Song Li","doi":"10.1021/cbe.4c00008","DOIUrl":"10.1021/cbe.4c00008","url":null,"abstract":"<p><p>Adsorption desalination (AD) driven by low-grade renewable energy or waste heat is a sustainable solution to the water crisis. Recently, metal-organic frameworks (MOFs) with excellent water adsorption performances have been recognized as some of the most promising candidates for AD. However, previous studies mainly focused on MOFs in powder form, causing pipe clogging and a drastic pressure drop, which inspire the development of shaped MOFs for industrial use. In this work, MIL-100(Fe) with high water stability, high adsorption capacity, and mild synthesis conditions was chosen, and the optimal formulation of the shaped MIL-100(Fe) granules using different binders was explored. The high-performing MIL-100(Fe)@5PVB granule containing 5% polyvinyl butyral (PVB) with outstanding adsorption performance and mechanical strength was selected and massively prepared for AD system testing. It is found that, although binder content decreased the surface area, pore volume, and water uptake of MIL-100(Fe), the mechanical strength and adsorption kinetics of shaped MIL-100(Fe)@5PVB were enhanced, which favor its performance in an AD system. Moreover, system testing demonstrated that the desalination performance of the AD system based on the adsorption beds of MIL-100(Fe)@5PVB outperformed both silica gel and MIL-100(Fe) powder. The specific daily water production (SDWP) of the AD system based on MIL-100(Fe)@5PVB (28.74 m³/ton/day) is 30% higher than that based on MIL-100(Fe) powder (19 m³/ton/day). Such a phenomenon is mainly contributed by the improved water adsorption dynamics of MIL-100(Fe)@5PVB granules that favors the mass transfer efficiency in the adsorption bed. This work opens up the possibility for the development of high-performing shaped MOFs for adsorption desalination from the perspectives of formulation optimization and system testing.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 10","pages":"817-825"},"PeriodicalIF":0.0,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11835254/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143461443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recent Progress in 3D Printing of Polymer Materials as Soft Actuators and Robots","authors":"Xiangren Kong,&nbsp;Min Dong,&nbsp;Miao Du,&nbsp;Jin Qian,&nbsp;Jun Yin,&nbsp;Qiang Zheng and Zi Liang Wu*,&nbsp;","doi":"10.1021/cbe.4c00028","DOIUrl":"10.1021/cbe.4c00028","url":null,"abstract":"<p >With inspiration from natural systems, various soft actuators and robots have been explored in recent years with versatile applications in biomedical and engineering fields. Soft active materials with rich stimulus-responsive characteristics have been an ideal candidate to devise these soft machines by using different manufacturing technologies. Among these technologies, three-dimensional (3D) printing shows advantages in fabricating constructs with multiple materials and sophisticated architectures. In this Review, we aim to provide an overview of recent progress on 3D printing of soft materials, robotics performances, and representative applications. Typical 3D printing techniques are briefly introduced, followed by state-of-the-art advances in 3D printing of hydrogels, shape memory polymers, liquid crystalline elastomers, and their hybrids as soft actuators and robots. From the perspective of material properties, the commonly used printing techniques and action-generation principles for typical printed constructs are discussed. Actuation performances, locomotive behaviors, and representative applications of printed soft materials are summarized. The relationship between printing structures and action performances of soft actuators and robots is also briefly discussed. Finally, the advantages and limitations of each soft material are compared, and the remaining challenges and future directions in this field are prospected.</p>","PeriodicalId":100230,"journal":{"name":"Chem & Bio Engineering","volume":"1 4","pages":"312–329"},"PeriodicalIF":0.0,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/cbe.4c00028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140689691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}