Coherent structures and wavepackets in subsonic transitional turbulent jets

A large eddy simulation (LES) is performed for two subsonic jets with a Reynolds number of , which have different core temperatures, i.e., the cold and hot jet. The far-field overall sound pressure levels (OASPL) and noise spectra are well validated against previous experimental results. It is found that the OASPL is raised by heating at shallow angles. The most energetic coherent structures are extracted with specified frequencies using the filter based on the frequency domain variant of the snapshot method of proper orthogonal decomposition (POD). The modes have high coherence of near-field pressure for both jets, while the coherence of modes is enhanced greatly by heating. Based on the coherent structures, spatial wavepackets are educed and the characteristics of growth, saturation and decay are analyzed and compared between the two jets in detail. The results show that heating would enhance the linear growth rate for high frequency components, and nonlinear growth rates for low frequency components in general, which are responsible for higher OASPL in the hot jet. The far-field sound generated by wavepackets is computed using the Kirchhoff extrapolation, which matches well with that of LES at shallow angles. This indicates that the wavepackets associated with coherent structures are dominant sound sources in forced transitional turbulent jets. Additionally, the present POD method is proven to be a robust tool to extract the salient features of the wavepackets in turbulent flows.

PD-L1-driven efficient enrichment and elimination of circulating cancer cells by magnetic MoSe_(2) nanosheet

Circulating tumor cells(CTCs)are important biomarkers in the development and progression of lung cancer because they can reach other organs through the blood circulation and form distant metastases,exacerbating lung cancer progression.The presence of CTCs is also the main reason for the failure of nanomedicine-based lung cancer treatments.Therefore,magnetic MoSe_(2) nanosheets loaded with programmed death-ligand 1(PD-L1),named PD-L1-MFP NS,were employed here to precisely capture lung cancer CTCs in the blood circulation through the tumor-targeting effect of PD-L1 killing CTCs with highly effective photothermal therapy(PTT).In addition,by increasing the expression of cytomegalovirus UL16-binding protein(ULBP)ligands on tumor cells,the PD-L1-MFP NS further activated natural killer(NK)cells and triggered NK cell-induced cancer immunotherapy,thereby enhancing the overall tumor-killing effect.In summary,this material designed to capture CTCs provides a substantial advancement for personalized PTT-triggered immunotherapy and has great clinical translational potential.

Fluoride passivation of ZnO electron transport layers for efcient PbSe colloidal quantum dot photovoltaics

Lead selenide(PbSe)colloidal quantum dots(CQDs)are suitable for the development of the next-generation of photovoltaics(PVs)because of efcient multiple-exciton generation and strong charge coupling ability.To date,the reported high-efcient PbSe CQD PVs use spin-coated zinc oxide(ZnO)as the electron transport layer(ETL).However,it is found that the surface defects of ZnO present a difculty in completion of passivation,and this impedes the continuous progress of devices.To address this disadvantage,fuoride(F)anions are employed for the surface passivation of ZnO through a chemical bath deposition method(CBD).The F-passivated ZnO ETL possesses decreased densities of oxygen vacancy and a favorable band alignment.Benefting from these improvements,PbSe CQD PVs report an efciency of 10.04%,comparatively 9.4%higher than that of devices using sol-gel(SG)ZnO as ETL.We are optimistic that this interface passivation strategy has great potential in the development of solution-processed CQD optoelectronic devices.

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.

Creation and erasure of polar bubble domains in PbTiO_(3)films by mechanical stress and light illuminations

The controllable manipulation of polar topological structures(e.g.skyrmion bubble)in ferroelectric materials have been considered as a cornerstone for future programmable nano-electronics.Here,we present the effective creation and erasure of polar bubble states PbTiO_(3)(PTO)multilayers trigged by mechanical stress and light illumination,respectively.It was found that applying atomic force microscope(AFM)tip force can induced formation of nanoscale bubble domains from the initial monodomain state.Moreover,the created bubble domain can be eliminated by exposure to ultraviolet or infrared light illumination.The above results can be understood by modulation of depolarization screening charges and bias fields,as reflected by scanning Kelvin potential microscopic(SKPM)observations,whereby the flexoelectric effect from the tip force tends to remove the screening charges on top surface and modulate the bias field that favors the formation of bubble state while light illumination tends to recover the screen charges and favor the monodomain state.The results provide a good example for multi-field manipulation of polar topologies,which might create a new avenue towards the immerging new concept electronic devices.

An improved long-term correlation tracking method with occlusion handling

By improving the long-term correlation tracking(LCT) algorithm, an effective object tracking method, improved LCT(ILCT), is proposed to address the issue of occlusion. If the object is judged being occluded by the designed criterion, which is based on the characteristic of response value curve, an added re-detector will perform re-detection, and the tracker is ordered to stop. Besides, a filtering and adoption strategy of re-detection results is given to choose the most reliable one for the re-initialization of the tracker. Extensive experiments are carried out under the conditions of occlusion, and the results demonstrate that ILCT outperforms some state-of-the-art methods in terms of accuracy and robustness.

PlantcircBase： A Database for Plant Circular RNAs

Dear Editor Circular RNAs （circRNAs） are a kind of non-coding RNAs; they were first found over 35 years ago but have only become a research hotspot in recent years. CircRNAs are covalently closed loops derived from precursor mRNAs by non-sequential back-splicing. Based on their genomic location, circRNAs can be classified into exonic, intronic, intergenic, and exon-intronic circRNAs （Chen, 2016）. By taking advantages of recent advances in bioinformatics algorithms, a large number of circRNAs have been detected among diverse organisms,