3D printing in space:from mechanical structures to living tissues

3D printing stands at the forefront of transforming space exploration,offering unprecedented on-demand and rapid manufacturing capabilities.It adeptly addresses challenges such as mass reduction,intricate component fabrication,and resource constraints.Despite the obstacles posed by microgravity and extreme environments,continual advancements underscore the pivotal role of 3D printing in aerospace science.Beyond its primary function of producing space structures,3D printing contributes significantly to progress in electronics,biomedicine,and resource optimization.This perspective delves into the technological advantages,environmental challenges,development status,and opportunities of 3D printing in space.Envisioning its crucial impact,we anticipate that 3D printing will unlock innovative solutions,reshape manufacturing practices,and foster self-sufficiency in future space endeavors.

3D printing of functional bioengineered constructs for neural regeneration: a review

Three-dimensional(3D)printing technology has opened a new paradigm to controllably and reproducibly fabricate bioengineered neural constructs for potential applications in repairing injured nervous tissues or producing in vitro nervous tissue models.However,the complexity of nervous tissues poses great challenges to 3D-printed bioengineered analogues,which should possess diverse architectural/chemical/electrical functionalities to resemble the native growth microenvironments for functional neural regeneration.In this work,we provide a state-of-the-art review of the latest development of 3D printing for bioengineered neural constructs.Various 3D printing techniques for neural tissue-engineered scaffolds or living cell-laden constructs are summarized and compared in terms of their unique advantages.We highlight the advanced strategies by integrating topographical,biochemical and electroactive cues inside 3D-printed neural constructs to replicate in vivo-like microenvironment for functional neural regeneration.The typical applications of 3D-printed bioengineered constructs for in vivo repair of injured nervous tissues,bio-electronics interfacing with native nervous system,neural-on-chips as well as brain-like tissue models are demonstrated.The challenges and future outlook associated with 3D printing for functional neural constructs in various categories are discussed.

Numerical investigation of airborne transmission of respiratory infections on the subway platform

Underground subway platforms are among the world’s busiest public transportation systems,but the airborne transmission mechanism of respiratory infections on these platforms has been rarely studied.Here,computational fluid dynamics(CFD)modeling is used to investigate the airflow patterns and infection risks in an island platform under two common ventilation modes:Mode 1-both sides have air inlets and outlets;Mode 2-air inlets are present at the two sides and outlets are present in the middle.Under the investigated scenario,airflow structure is characterized by the ventilation jet and human thermal plumes.Their interaction with the infector’s breathing jet imposes the front passenger under the highest exposure risk by short-range airborne route,with intake fractions up to 2.57%(oral breathing)or 0.63%(nasal breathing)under Mode 1;oral breathing of the infector may impose higher risks for the front passenger compared with nasal breathing.Pathogen are efficiently diluted as they travel further,in particular to adjacent crowds.The maximum and median value of intake fractions of passengers in adjacent crowds are respectively 0.093%and 0.016%(oral breathing),and 0.073%and 0.014%(nasal breathing)under Mode 1.Compared with Mode 1,the 2nd mode minimizes the interaction of ventilation jet and breathing jet,where the maximum intake fraction is only 0.34%,and the median value in the same crowd and other crowds are reduced by 23–63%.Combining published quanta generation rate data of COVID-19 and influenza infectors,the predicted maximum and median infection risks for passengers in the same crowds are respectively 1.46%–40.23%and 0.038%–1.67%during the 3–10 min waiting period,which are more sensitive to ventilation rate and exposure time compared with return air.This study can provide practical guidance for the prevention of respiratory infections in subway platforms.

Bioconversion of lignocellulosic biomass into bacterial nanocellulose:challenges and perspectives

Nanocellulose has various outstanding properties and great potential for replacing petrochemical products.The utilization of lignocellulose to produce nanocellulose is of great significance to the sustainable development of the economy and society.However,the direct extraction of nanocellulose from lignocellulose by chemical method is challenged by toxic chemicals utilization,energy and time consumption,and waste water generation.Therefore,this paper addressed the conversion of lignocellulosic biomass into bacterial nanocellulose(BNC)by the biological method.Moreover,this article highlights the recent advances in potentials and challenges of lignocellulosic biomass for BNC production through the bioconversion process,including biomass pretreatment,enzymatic hydrolysis,glucose and xylose fermentation,GA accumulation,and inhibitor tolerant.The development in metabolic and evolutionary engineering to enhance the production capacity of BNC-producing strain is also discussed.It is expected to provide guidance on the effective bioproduction of nanocellulose from lignocellulosic biomass.

A CRISPR activation screen identifies genes that enhance SARS-CoV-2 infection

Dear Editor,Identifying the host factors that are utilized for virus infection and mapping their cell-type expression profile can help to understand the viral tissue/organ tropism and pathogenesis.Much effort has been devoted to the identification of SARS-CoV-2 infection-dependent host factors.CRISPR-based activation(Konermann et al.,2015).

通过溶剂蒸汽处理制备多级静电纺丝纳米纤维作为空气过滤膜实现PM2.5高效捕获（英文）

空气污染特别是颗粒物(PM)污染,已经威胁到人类的身体健康,因而引起了全世界的高度关注.人们在室外可通过口罩进行个人防护,然而一般的商业口罩起不到好的防护效果.本文利用静电纺丝技术和溶剂蒸汽退火(SVA)方法制备了新型高效的聚(ε-己内酯)/聚环氧乙烷(PCL/PEO)空气过滤纳米纤维.通过SVA处理,纤维表面变得褶皱,增强了对PM2.5的捕获效率.在重度污染状况(PM2.5颗粒浓度>225 mg m^(-3))下,这种纳米褶皱空气过滤膜的移除效率达80.01%.秦皇岛雾霾天实地测量表明,空气过滤膜能高效移除PM2.5.与商业口罩相比,本文经过SVA处理后的PCL/PEO空气过滤膜具有制备方法简单、环境友好且易降解的特性,在高效过滤膜领域有潜在应用.

Sphingosine-1-phosphate,a novel TREM2 ligand,promotes microglial phagocytosis to protect against ischemic brain injury

The mechanism of sphingosine-1-phosphate(S1P)-mediated phagocytosis remains unknown.Here,we found that S1P or FTY720(an analog of S1P)promoted microglial phagocytosis in stroke independent of S1PRs.First,we used computer simulation of molecular docking to predict that S1P might be a ligand for triggering receptor expressed on myeloid cells 2(TREM2).Next,microscale thermophoresis(MST),surface plasmon resonance(SPR)and liquid chromatography–tandem mass spectrometry(LC–MS/MS)were performed to reveal that S1P was a novel TREM2 ligand.Then,we confirmed the pro-phagocytosis of S1P targeting in Trem2-Dap12 transfected CHO cells and TREM2 knockdown microglia.Point mutation analysis showed that D104 was the critical binding residue.Trem2^(−/−)mice were used to demonstrate the role of S1P-induced phagocytosis targeting on TREM2 in protecting against ischemic brain injury.Finally,further studies revealed that apolipoprotein E(APOE)loaded with S1P was released by microglia and bound to apoptotic neurons via LDL receptor related protein 1B(LRP1B)and thereby induced microglia to phagocytose apoptotic neurons.Overall,the present work reveals for the first time that S1P acts as a novel endogenous ligand of TREM2 to effectively promote microglial phagocytosis.Our findings provide a new lead compound for developing immunomodulator targeting on TREM2.

EasySVM: A visual analysis approach for open-box support vector machines

Support vector machines(SVMs) are supervised learning models traditionally employed for classification and regression analysis. In classification analysis, a set of training data is chosen, and each instance in the training data is assigned a categorical class. An SVM then constructs a model based on a separating plane that maximizes the margin between different classes. Despite being one of the most popular classification models because of its strong performance empirically, understanding the knowledge captured in an SVM remains difficult. SVMs are typically applied in a black-box manner where the details of parameter tuning, training, and even the final constructed model are hidden from the users. This is natural since these details are often complex and difficult to understand without proper visualization tools. However, such an approach often brings about various problems including trial-and-error tuning and suspicious users who are forced to trust these models blindly.The contribution of this paper is a visual analysis approach for building SVMs in an open-box manner.Our goal is to improve an analyst's understanding of the SVM modeling process through a suite of visualization techniques that allow users to have full interactive visual control over the entire SVM training process.Our visual exploration tools have been developed to enable intuitive parameter tuning, training datamanipulation, and rule extraction as part of the SVM training process. To demonstrate the efficacy of our approach, we conduct a case study using a real-world robot control dataset.

非“三明治”结构的分子基光电器件

传统的分子材料光电器件如太阳能电池和有机发光二极管通常采用"三明治"型垂直结构.器件通常由透明底电极、薄膜活性层和顶接触电极构成.该结构优化了光与半导体的相互作用以及载流子的注入和收集,实际应用广泛.近些年,为了降低透明电极的使用成本以及更好地实现非薄膜形态纳米半导体材料的器件构筑,一些非"三明治"结构的有机光电器件也取得了很大进展:发展出了具有微米、纳米电极结构的光伏器件、光电导器件、光晶体管器件、纳米间隙电极器件等,拓展了分子基光电材料的应用研究,与传统夹心型二极管器件相互补充、相互完善.本文主要聚焦在各种非"三明治"结构有机光电器件的构筑与功能化,对有代表性的研究成果进行了总结与评述,并对其未来的发展进行了展望.

In memory of Hal E.Broxmeyer,a pluripotent scientist,pioneer,and mentor

With great sadness,we residing in China heard the news that Professor Hal E.Broxmeyer passed away on December 8,2021,due to complications of thyroid cancer.He was 77.We regret that we could not say goodbye in person to Hal,as he was fondly called by his students and colleagues around the world.We wish to express publicly our heartfelt gratitude to Hal for his many seminal contributions to the scientific research and applications,and profound impact on the careers of younger scientists like us.We are sure that our feeling and gratitude are also shared by hundreds of youngsters who are fortunate to have interactions with Hal.He will continue to be a bright star in the sky,inspiring and guiding us for many years to come.