Patterning of large area nanoscale domains in as-grown epitaxial ferroelectric PbTiO_(3)films

Effective tuning of nanoscale domain structures provides fundamental basis for controlling and engineering of various functionalities in ferroelectric materials.In this work,we demonstrate the precise patterning of nanoscopic domain structures in as-grown epitaxial PbTiO_(3)(PTO)films by merely introducing an ultrathin pre-patterned doping layer(e.g.,Fe-doped PTO).The doping layer can effectively reverse the interfacial built-in bias,consequent to a reversed initial polarization reorientation in the as-grown film,which makes it possible to transfer the nano-patterns in the doping layer into the domain structure of ferroelectric films.For instance,we have successfully fabricated large area ordered array of nanoscale cylindrical domains(downward polarization)embedded in the matrix domain with opposite polarization(upward polarization)in PTO film.These nanoscale cylinder domains also allow deterministic and reversible erasure and creation induced by biased tip scanning.The results provide an effective pathway for on-demand patterning of large area nanoscale domains in the as-grown films,which may find applications in a wide range of nanoelectronic devices.

Seasonal hydrological dynamics govern lifestyle preference of aquatic antibiotic resistome

Antibiotic resistance genes(ARGs)are a well-known environmental concern.Yet,limited knowledge exists on the fate and transport of ARGs in deep freshwater reservoirs experiencing seasonal hydrological changes,especially in the context of particle-attached(PA)and free-living(FL)lifestyles.Here,the ARG profiles were examined using high-throughput quantitative PCR in PA and FL lifestyles during four seasons representing two hydrological phenomena(vertical mixing and thermal stratification)in the Shuikou Reservoir(SR),Southern China.The results indicated that seasonal hydrological dynamics were critical for influencing the ARGs in PA and FL and the transition of ARGs between the two lifestyles.ARG profiles both in PA and FL were likely to be shaped by horizontal gene transfer.However,they exhibited distinct responses to the physicochemical(e.g.,nutrients and dissolved oxygen)changes under seasonal hydrological dynamics.The particle-association niche(PAN)index revealed 94 non-conservative ARGs(i.e.,no preferences for PA and FL)and 23 and 16 conservative ARGs preferring PA and FL lifestyles,respectively.A sharp decline in conservative ARGs under stratified hydrologic suggested seasonal influence on the ARGs transition between PA and FL lifestyles.Remarkably,the conservative ARGs(in PA or FL lifestyle)were more closely related to bacterial OTUs in their preferred lifestyle than their counterparts,indicating lifestyle-dependent ARG enrichment.Altogether,these findings enhanced our understanding of the ARG lifestyles and the role of seasonal hydrological changes in governing the ARG transition between the lifestyles in a typical deep freshwater ecosystem.

在线直播教学模式在成人学历教育的应用研究

在线直播教学模式是指借助网络、直播软件平台及电子终端设备进行“教”与“学”活动的一种教学模式。在线直播教学模式突破了时空限制,它能减弱成人学生的工学矛盾。在线直播教学模式实现师生实时互动,解决了自学能力较弱、学习素养相对欠缺的成人学生在自主学习过程中因缺乏互动而导致学习兴趣不足的问题。在线直播教学模式在成人学历教育的应用满足了成人学生的需求,它有在成人学历教育应用的可能性、必要性而且意义重大。分析在线直播教学模式在成人教育应用中存在的问题,提出了在线直播教学在成人学历教育的几点应用策略。

Horizontal and vertical gene transfer drive sediment antibiotic resistome in an urban lagoon system

Rapid urbanization has resulted in pervasive occurrence of antibiotic resistance genes(ARGs)in urban aquatic ecosystems.However,limited information is available concerning the ARG profiles and the forces responsible for their assembly in urban landscape lagoon systems.Here,we employed high-throughput quantitative PCR(HT-q PCR)to characterize the spatial variations of ARGs in surface and core sediments of Yundang Lagoon,China.The results indicated that the average richness and absolute abundance of ARGs were 11 and 53 times higher in the lagoon sediments as compared to pristine reference Tibetan lake sediments,highlighting the role of anthropogenic activities in ARG pollution.Co-occurrence network analysis indicated that various anaerobic prokaryotic genera belonging to Alpha-,Deltaproteobacteria,Bacteroidetes,Euryarchaeota,Firmicutes and Synergistetes were the potential hosts of ARGs.The partial least squares-path modeling(PLS-PM)analysis revealed positive and negative indirect effects of physicochemical factors and heavy metals on the lagoon ARG profiles,via biotic factors,respectively.The horizontal(mediated by mobile genetic elements)and vertical(mediated by prokaryotic communities)gene transfer may directly contribute the most to drive the abundance and composition of ARGs,respectively.Furthermore,the neutral community model demonstrated that the assembly of sediment ARG communities was jointly governed by deterministic and stochastic processes.Overall,this study provides novel insights into the diversity and distribution of ARGs in the benthic habitat of urban lagoon systems and underlying mechanisms for the spread and proliferation of ARGs.