An Al–Al interpenetrating-phase composite by 3D printing and hot extrusion

We report a process route to fabricate an Al–Al interpenetrating-phase composite by combining the Al–Mg–Mn–Sc–Zr lattice structure and Al_(84)Ni_(7)Gd_(6)Co_(3)nanostructured structure. The lattice structure was produced by the selective laser melting and subsequently filled with the Al_(84)Ni_(7)Gd_(6)Co_(3)amorphous powder, and finally the mixture was used for hot extrusion to produce bulk samples. The results show that the composites achieve a high densification and good interface bonding due to the element diffusion and plastic deformation during hot extrusion.The bulk samples show a heterogeneous structure with a combination of honeycomb lattice structure with an average grain size of less than1 μm and nanostructured area with a high volume fraction of nanometric intermetallics and nanograin α-Al. The heterogeneous structure leads to a bimodal mechanical zone with hard area and soft area giving rise to high strength and acceptable plasticity, where the compressive yield strength and the compressive plasticity can reach ~745 MPa and ~30%, respectively. The high strength can be explained by the rule of mixture,the grain boundary strengthening, and the back stress, while the acceptable plasticity is mainly owing to the confinement effect of the nanostructured area retarding the brittle fracture behavior.

Towards understanding the mechanism of n-hexane tolerance in Synechocystis sp.PCC 6803

Synthetic biology efforts have also led to the development of photosynthetic cyanobacteria as"autotrophic cell factories"for biosynthesis of various biofuels directly from CO_(2).However,the low tolerance to toxicity of biofuels has restricted the economic application of cyanobacterial hosts.In this study,RNAseq transcriptomics was employed to reveal stress responses to exogenous n-hexane in Synechocystis sp.PCC 6803.Functional enrichment analysis of the transcriptomic data showed that signal transduction systems were induced significantly.To further identify regulatory genes related to n-hexane tolerance,a library of transcriptional regulators(TRs)deletion mutants was then screened for their roles in nhexane tolerance.The results showed that a knockout mutant of slr0724 that encodes an Hta R suppressor protein was more tolerant to n-hexane than the wild type,indicating the involvement of slr0724 in nhexane tolerance.This study provides the foundation for better understanding the cellular responses to n-hexane in Synechocystis sp.PCC 6803,which could contribute to the further engineering of nhexane tolerance in cyanobacteria.

Deciphering and engineering high-light tolerant cyanobacteria for efficient photosynthetic cell factories

Development and utilization of“liquid sunshine”could be one of key solutions to deal with the issues of fossil fuel depletion and increasing carbon dioxide.Cyanobacteria are the only prokaryotes capable of performing oxygenic photosynthesis,and their activity accounts for~25%of the total carbon fixation on earth.More importantly,besides their traditional roles as primary producers,cyanobacteria could be modified as“photosynthetic cell factories”to produce renewable fuels and chemicals directly from CO_(2) driven by solar energy,with the aid of cutting-edging synthetic biology technology.Towards their large-scale biotechnological application in the future,many challenges still need to be properly addressed,among which is cyanobacterial cell factories inevitably suffer from high light(HL)stress during large-scale outdoor cultivation,resulting in photodamage and even cell death,limiting their productivity.In this review,we critically summarized recent progress on deciphering molecular mechanisms to HL and developing HL-tolerant chassis in cyanobacteria,aiming at facilitating construction of HLresistant chassis and promote the future application of the large-scale outdoor cultivation of cyanobacterial cell factories.Finally,the future directions on cyanobacterial chassis engineering were discussed.

Influence of Fe-rich phases and precipitates on the mechanical behaviour of Al-Cu-Mn-Fe-Sc-Zr alloys studied by synchrotron X-ray and neutron

A multiscale methodology using scanning and transmission electron microscope,synchrotron X-ray nano-tomography and micro-tomography,small angle neutron scattering,and in situ synchrotron X-ray diffrac-tion has been used,to reveal the effect of Fe-rich phases and precipitates on the mechanical behaviour of an Al-Cu-Mn-Fe-Sc-Zr alloy.Theα-Al grains size is reduced from 185.1μm(0 MPa)and 114.3μm(75 MPa)by applied pressure.Moreover,it has been demonstrated that suitable heat treatments modify the 3D morphology of Fe-rich phases from interconnected to a disaggregated structure that improves the mechanical properties of the alloy.The size and morphology evolution of fine precipitates under differ-ent ageing temperature and time are revealed.At ageing temperature of 160℃,the precipitates change from GP zones toθ’(around 75 nm in length)with ageing time increasing from 1 h to 24 h;the Vick-ers hardness increases from 72.0 HV to 110.7HV.The high ductility of the Sc,Zr modified Al-Cu alloy is related to the complex shape and the loss of interconnectivity of the Fe-rich particles due to the heat treatment.The evolution of the crystal lattice strains inα-Al,andβ-Fe calculated during tensile test us-ing in-situ synchrotron X-ray diffraction corroborates the influence of the microstructure in the ductility of the modified alloy.

Human genome editing after the "CRISPR babies":The double-pacing problem and collaborative governance

How to ensure the safe,effective,and ethical use of emerging biotechnologies,such as clustered regularly interspaced short palindromic repeats(CRISPR)-based genome editing,is a global challenge.The occurrence of the"CRISPR babies"in 2018 publicly brought this issue into sharp focus,and led to comprehensive regulatory reforms in China and various countries around the world.The current article analyzes this event-driven regulatory reform in China by elaborating the most salient provisions designed to prevent risk and protect individual rights,public health,and social morality relating to human genome editing in four important sectors of law:biosecurity law,civil code,criminal law and patent law.It highlights that,although regulation is being undertaken,the gaps between the law and advancing technology remain discernible,at both a national and transnational level(i.e.,the "double-pacing problem").Further attention and collaboration will be required to address the ongoing challenges associated with the use of human genome editing.

耕地非农化严格管控下的地方合作、共谋与制度创新——源自浙江省土地发展权折抵指标交易政策的证据

在中国式央地分权结构下,地方政府具有相当的自由裁量权,从而基于地方利益选择相互竞争还是合作,甚至竞次或者共谋。本文以地方政府为获取超额建设占用耕地指标而创立的土地发展权折抵交易政策为例,提出了经济层面地方合作乃至共谋可能性的假说,并借助1999—2008年间浙江省的土地折抵指标交易数据进行实证检验。结果发现,经济发展水平差距、资源禀赋差距和人缘网络关系显著影响地方政府间通过交易共谋超额建设占用耕地指标的概率。本文的研究为解释中国式分权化改革后地方政府行为的逻辑提供了新的视角和实证依据。

Challenges and recent progress in the governance of biosecurity risks in the era of synthetic biology

Considerable progress has been achieved in basic research and the biotechnological application of biological sciences in recent years.Synthetic biology integrates systems biology,engineering,computer science,and other disciplines to achieve the“modification of life”or even the“creation of life”via the redesign of existing natural systems or the development of new biological components and devices.However,the research and application of synthetic biology can create potential risks,such as aggravation of species with complex gene modifications,threats to species diversity,abuse of biological weapons,laboratory leaks,and man-made mutations.Without a suitable governance system,such research activities could result in harm to humans,plants,and animals,as well as to natural ecological systems.In this article,we first briefly summarize technical progress in synthetic biology in recent years and the potential bioethical and biosecurity risks,and then describe current international treaties,guidance documents,and national regulatory measures designed to address potential harm caused by the dual-use property of synthetic biology,including the Biological Weapons Convention,the Convention on Biological Diversity,and the Model Code of Conduct for Biological Scientists(Tianjin Biosecurity Guidelines for Codes of Conduct for Scientists).In addition,we also present some recommendations for better governance of synthetic biology research and applications in China,including strengthening the biosecurity capacity,improving the biosecurity regulatory system,and promoting multilevel international cooperation to effectively address the potential biosecurity risks of synthetic biology.

Processing of AZ31 magnesium alloy by accumulative roll-bonding at gradient temperature

In the present investigation a wrought magnesium alloy AZ31 was successfully processed by the accumulative roll-bonding （ARB） at gradient temperature up to six cycles with the lowest temperature of 250 °C. This is performed through different thermomechanical processing routes （different ARB cycles at different temperatures of 350-200 °C）. The microstructures and mechanical properties were investigated. The results indicate that significant grain refinement is observed after the first two cycles at the highest ARB temperature as a result of dynamic recrystallization, which is necessary for the subsequently ARB cycles at relatively lower temperature with the aim to restrict grain growth. No significant finer grain size was observed through the fifth and sixth cycles while the microstructure homogeneity is further improved. The grain structure can be effectively refined at lower ARB processing temperature and higher cycles. The resulting material exhibited high strength and relatively high ductility at ambient temperature when ARB deformed above 250 °C. The mechanical properties of the ARB deformed materials are strongly dependent on several main factors： the amount and the homogeneity of strain achieved, grain size and microstructure homogeneity, textures developed during ARB and interface bonding quality.

Tailoring microstructure and texture of Mg-3Al-1Zn alloy sheets through curve extrusion process for achieving low planar anisotropy

Curve extrusion processes,including symmetric curve extrusion(SCE)and asymmetric curve extrusion(ACE)processes,were proposed to fabricate Mg-3Al-1Zn(AZ31)alloy sheets with the aim of improving planar anisotropy.For comparison,traditional extrusion(TE)was conducted on producing AZ31 sheets.The dynamic recrystallization and flow behavior of AZ31 Mg alloy during extrusion were examined and analyzed,and the final microstructures and mechanical properties of AZ31 sheets were investigated.In comparison with the TE sheet,finer grain size,more uniform microstructure and weaker tilted basal tex-ture were achieved in the SCE and ACE sheets.Both the SCE and ACE sheets exhibited unique textures which basal poles tilted to extrusion direction(ED)and new transverse direction(TD)-tilted texture com-ponent was developed.The reasons were mainly ascribed to the introduction of additional flow velocity difference along TD during extrusion.Furthermore,the ACE sheet exhibited the lowest basal pole inten-sity,which was attributed to the introduction of extra asymmetric shear deformation during extrusion process.As a result,the ACE sheet showed the lowest yield strength and r-value,but highest elongation and n-value.Improving the planar anisotropy of AZ31 sheet was achieved by the ACE process.

Tianjin Biosecurity Guidelines for codes of conduct for scientists:Promoting responsible sciences and strengthening biosecurity governance

Formulated and endorsed by the international scientific community,the Tianjin Biosecurity Guidelines are a set of ten guiding principles and standards of conduct designed to promote responsible sciences and strengthen biosecurity governance at national and institutional levels.It may be used to develop new or enhance,supplement,and update the existing codes of conduct adaptive to a specific context and responsive to the bio-risks arising from the rapid advances in biological sciences.

Synthetic biology:Recent progress,biosafety and biosecurity concerns,and possible solutions

Synthetic biology is a new interdisciplinary research area that uses engineering principles as guidelines for biological investigation.With research goals to modify existing biological systems or to create new ones,the recent applications of synthetic biology have expanded approaches and tools for conventional biological research.In this article,we first briefly review the development and progress of synthetic biology over the past decade.Although the contributions of synthetic biology to basic life science research,human health,environmental protection,and even economic growth have been widely observed,potential biosafety,biosecurity,and ethical risks related to synthetic biology have also emerged in recent years as technology becomes less expensive,more mature,and more accessible.We provide a brief assessment of the risks associated with the possible misuse or abuse of this technology in various areas and discuss concerns from three points of view:biosafety,biosecurity risks,and ethics.Finally,to address challenges arising from the rapid progress of synthetic biology,technical,ethical,and regulatory measures were developed or discussed in recent years,including laboratory level precautionary measures for biosafety and biosecurity related to synthetic biology(such as genetic safeguards and firewalls),ethical codes of conduct for biological scientists,and regulations or oversight rules from personal,national,and international perspectives.A brief summary of these efforts is provided.

Building and implementing a multi-level system of ethical code for biologists under the Biological and Toxin Weapons Convention(BTWC)of the United Nations

The recent global COVID-19 pandemic has had profound economic and social impacts on the world.It has highlighted an urgent need to strengthen existing international biosecurity governance mechanisms to prevent the misuse and malicious abuse of life science research and maintain international biological arms control norms.Biologists are at the front line of biotechnology development and are key to maintaining biosecurity awareness and moral self-discipline.As an important first step,biologists need to actively participate in the formulation and implementation of relevant biosecurity policies and measures to ensure their effectiveness and sustainability.Furthermore,efforts should be made to advocate for and promote the establishment of an ethical code of conduct for biologists to share safety responsibilities for global biosecurity.To maximize the impact of this ethical code of conduct,an effective approach to implementing codes of conduct for biologists at both national and international levels should be established under the framework of the Biological and Toxin Weapons Convention(BTWC).

Nucleation and growth of Fe-rich phases in Al-5Ti-1B modified Al-Fe alloys investigated using synchrotron X-ray imaging and electron microscopy

Plate-like Fe-rich intermetallic phases directly influence the mechanical properties of recycled Al alloys;thus, many attempts have been made to modify the morphology of these phases. Through synchrotron X-ray imaging and electron microscopy, the underlying nucleation and growth mechanisms of Fe-rich phases during the solidification of Al-5 Ti-1 B-modified Al-2 Fe alloys were revealed in this study. The results showed that the Al-5 Ti-1 B grain refiner as well as the applied pressure both resulted in reduction of the size and number of primary Al_(3)Fe phases and promoted the formation of eutectic Al_(6)Fe phases.The tomography results demonstrated that Al-5 Ti-1 B changed the three-dimensional(3 D) morphology of primary Fe-rich phases from rod-like to branched plate-like, while a reduction in their thickness and size was also observed. This was attributed to the fact that Ti-containing solutes in the melts inhibit the diffusion of Fe atoms and the Al_(3)Fe twins produce re-entrant corner on the twin boundaries along the growth direction. Moreover, the TiB_(2) provides possible nucleation sites for Al_6Fe phases. The nucleation mechanism of Fe-rich phases is discussed in terms of experimental observations and crystallography calculations. The decrease in the lattice mismatch between TiB_(2) and Al_(6)Fe phases was suggested, which promoted the transformation of Al_(3)Fe to Al_(6)Fe phases.

Improving entity linking with two adaptive features

Entity linking(EL)is a fundamental task in natural language processing.Based on neural networks,existing systems pay more attention to the construction of the global model,but ignore latent semantic information in the local model and the acquisition of effective entity type information.In this paper,we propose two adaptive features,in which the first adaptive feature enables the local and global models to capture latent information,and the second adaptive feature describes effective information for entity type embeddings.These adaptive features can work together naturally to handle some uncertain entity type information for EL.Experimental results demonstrate that our EL system achieves the best performance on the AIDA-B and MSNBC datasets,and the best average performance on out-domain datasets.These results indicate that the proposed adaptive features,which are based on their own diverse contexts,can capture information that is conducive for EL.

Genome editing and human rights:Implications of the UNGPs

How to address the impact of genome editing on human rights is a global challenge.The World Health Organization(WHO)recently developed a governance framework for human genome editing to provide global recommendations for establishing appropriate governance mechanisms for human genome editing.This article suggests that a human rights-respecting approach should be explicitly recognized in the framework and other relevant endeavors.Such recognition has significant implications not only on clarifying the duty of States but also on the responsibility of non-State actors,particularly biotech enterprises,to orient this technology towards respect for human rights.To implement this approach,the United Nations Guiding Principles on Business and Human Rights(UNGPs)provide helpful guidance for States,biotech enterprises,and other stakeholders to raise awareness and enhance responsible practices in the field.

Biosafety and biosecurity in the era of synthetic biology:Meeting the challenges in China and the U.S.

On July 26,2019,the workshop “Biosafety and Biosecurity in the Era of Synthetic Biology:Meeting the Challenges in China and the U.S.”,co-hosted by Johns Hopkins Center for Health Security and Tianjin University Centre for Biosafety Research&Strategy,was held in Washington,D.C.of the United States.The goal of this workshop was to bring technical and policy experts from China and the U.S.,as well as experts from Europe,together to develop a mutual understanding of each country’s current governance structures and to begin a dialogue on what is required to promote global biosafety and biosecurity.