Experimental study on hydrodynamic behaviors of high-speed gas jets in still water

The present paper describes experimental investigation on the flow pattern and hydrodynamic effect of underwater gas jets from supersonic and sonic nozzles operated in correct- and imperfect expansion conditions. The flow visualizations show that jetting is the flow regime for the submerged gas injection at a high speed in the parameter range under consideration. The obtained results indicate that high-speed gas jets in still water induce large pressure pulsations upstream of the nozzle exit and the presence of shock-cell structure in the over- and under-expanded jets leads to an increase in the intensity of the jet-induced hydrodynamic pressure.

Developing single nucleotide polymorphism(SNP)markers from transcriptome sequences for identification of longan(Dimocarpus longan)germplasm

Longan(Dimocarpus longan Lour.)is an important tropical fruit tree crop.Accurate varietal identification is essential for germplasm management and breeding.Using longan transcriptome sequences from public databases,we developed single nucleotide polymorphism(SNP)markers;validated 60 SNPs in 50 longan germplasm accessions,including cultivated varieties and wild germplasm;and designated 25 SNP markers that unambiguously identified all tested longan varieties with high statistical rigor(P<0.0001).Multiple trees from the same clone were verified and off-type trees were identified.Diversity analysis revealed genetic relationships among analyzed accessions.Cultivated varieties differed significantly from wild populations(Fst=0.300;P<0.001),demonstrating untapped genetic diversity for germplasm conservation and utilization.Within cultivated varieties,apparent differences between varieties from China and those from Thailand and Hawaii indicated geographic patterns of genetic differentiation.These SNP markers provide a powerful tool to manage longan genetic resources and breeding,with accurate and efficient genotype identification.

Developing single nucleotide polymorphism markers for the identification of pineapple(Ananas comosus)germplasm

Pineapple(Ananas comosus[L.]Merr.)is the third most important tropical fruit in the world after banana and mango.As a crop with vegetative propagation,genetic redundancy is a major challenge for efficient genebank management and in breeding.Using expressed sequence tag and nucleotide sequences from public databases,we developed 213 single nucleotide polymorphism(SNP)markers and validated 96 SNPs by genotyping the United States Department of Agriculture-Agricultural Research Service pineapple germplasm collection,maintained in Hilo,Hawaii.The validation resulted in designation of a set of 57 polymorphic SNP markers that revealed a high rate of duplicates in this pineapple collection.Twenty-four groups of duplicates were detected,encompassing 130 of the total 170 A cosmos accessions.The results show that somatic mutation has been the main source of intra-cultivar variations in pineapple.Multivariate clustering and a model-based population stratification suggest that the modern pineapple cultivars are comprised of progenies that are derived from different wild Ananas botanical varieties.Parentage analysis further revealed that both A.comosus var.bracteatus and A.comosus var.ananassoides are likely progenitors of pineapple cultivars.However,the traditional classification of cultivated pineapple into horticultural groups(e.g.‘Cayenne’,‘Spanish’,‘Queen’)was not well supported by the present study.These SNP markers provide robust and universally comparable DNA fingerprints;thus,they can serve as an efficient genotyping tool to assist pineapple germplasm management,propagation of planting material,and pineapple cultivar protection.The high rate of genetic redundancy detected in this pineapple collection suggests the potential impact of applying this technology on other clonally propagated perennial crops.

Two-way coupling model for shock-induced laminar boundary-layer flows of a dusty gas

The present paper describes a numerical two-way coupling model for shock-induced laminar boundary-layer flows of a dust-laden gas and studies the transverse migration of fine particles under the action of Saffman lift force. The governing equations are formulated in the dilute twophase continuum framework with consideration of the finiteness of the particle Reynolds and Knudsen numbers. The full Lagrangian method is explored for calculating the dispersedphase flow fields （including the number density of particles） in the regions of intersecting particle trajectories. The computation results show a significant reaction of the particles on the two-phase boundary-layer structure when the mass loading ratio of particles takes finite values.

A Decreasing Upper Bound of the Energy for Time-Fractional Phase-Field Equations

In this article,we study the energy dissipation property of time-fractional Allen–Cahn equation.On the continuous level,we propose an upper bound of energy that decreases with respect to time and coincides with the original energy at t=0 and as t tends to∞.This upper bound can also be viewed as a nonlocal-in-time modified energy which is the summation of the original energy and an accumulation term due to the memory effect of time-fractional derivative.In particular,the decrease of the modified energy indicates that the original energy indeed decays w.r.t.time in a small neighborhood at t=0.We illustrate the theory mainly with the time-fractional Allen-Cahn equation but it could also be applied to other time-fractional phase-field models such as the Cahn-Hilliard equation.On the discrete level,the decreasing upper bound of energy is useful for proving energy dissipation of numerical schemes.First-order L1 and second-order L2 schemes for the time-fractional Allen-Cahn equation have similar decreasing modified energies,so that stability can be established.Some numerical results are provided to illustrate the behavior of this modified energy and to verify our theoretical results.

Achieving high thermoelectric performance through carrier concentration optimization and energy filtering in Cu_(3)SbSe_(4)-based materials

The previous works commonly adjust the carrier concentration through acceptor doping,but at the same time,the decrease of the Seebeck coefficient limits the further improvement of electrical properties in Cu_(3)SbSe_(4)-based materials.In this work,a microwave-assisted hydrothermal synthesis method was used to synthesize Cu_(3)SbSe_(4)/TiO_(2) hollow microspheres.Part of TiO_(2) participates in the reaction,replaces the Sb site of Cu_(3)SbSe_(4) to form holes,and the rest is dispersed in the matrix in the form of the second phase.The first-principles calculations reveal that the doping of Ti significantly changes the band structure and phonon spectrum,thereby regulating carrier concentration while increasing phonon scattering.In addition,experimental results show that the energy filtering effect generated by the extra-mixed TiO_(2) nano particles,which suppresses the decrease of Seebeck coefficient by acceptor doping.Consequently,the highest average power factor 897.5 mW m^(-1) K^(-2) and the zT peak value of 0.70 can be obtained in Cu_(3)SbSe_(4)/6%TiO_(2) sample at 298e623 K.This work provides a new sight to improve the thermoelectric properties in Cu_(3)SbSe_(4) through carrier concentration regulation and nano-phase composition.

Synergistic band convergence and defect engineering boost thermoelectric performance of SnTe

As an eco-friendly thermoelectric material,Sn Te has attracted extensive attention.In this study,we use a stepwise strategy to enhance the thermoelectric performance of Sn Te.Firstly,Ag Cl is doped into Sn Te to realize band convergence and enlarge the band gap of Ag Cl-doped Sn Te.Ag Cl-doping also induces dense point defects,strengthens the phonon scattering,and reduces the lattice thermal conductivity.Secondly,Sb is alloyed into Ag Cl-doped Sn Te to further optimize the carrier concentration and simultaneously reduce the lattice thermal conductivity,leading to improved thermoelectric dimensionless figure of merit,ZT.Finally,(Sn_(0.81)Sb_(0.19)Te)_(0.93)(Ag Cl)_(0.07)has approached the ZT value as high as~0.87 at 773 K,which is 272%higher than that of pristine Sn Te.This study indicates that stepwise Ag Cl-doping and Sb-alloying can significantly improve thermoelectric performance of Sn Te due to synergistic band engineering,carrier concentration optimization and defect engineering.

Decoupling of thermoelectric transport performance of Ag doped and Se alloyed tellurium induced by carrier mobility compensation

Alloying with Se is proved to be feasible to suppress the lattice thermal conductivity(κL)of tellurium by introducing multidimensional lattice defects.However,extra ionization impurity centers induced by Se alloying are harmful to the electric transport properties of the matrix.In this paper,we propose that the incorporation of Ag could successfully compensate the lost carrier mobility(μH)due to Se alloying through the regulation of microstructure,resulting in the higher power factor(PF)than that of samples without Ag.After composition optimization,theκLdecreased from 1.29 W m^(-1)K^(-1) of Te_(0.99)Sb_(0.01) to 1.05 W m^(-1)K^(-1) of Te_(0.94)Ag_(0.02)Se_(0.03)Sb_(0.01) at 350 K,while the PF remained unchanged or even slightly increased.Benefit from the synergistic effect of carrier mobility compensation and phonon scattering,a maximum z T of 0.91 at 573 K and an average z T of 0.57(between 298 and 573 K)are achieved in Te_(0.94)Ag_(0.02)Se_(0.03)Sb_(0.01).This work presents a new strategy for decoupling the thermal and electric parameters of Te-based thermoelectric materials.

A genetically engineered Escherichia coli that senses and degrades tetracycline antibiotic residue

Due to the abuse of antibiotics,antibiotic residues can be detected in both natural environment and various industrial products,posing threat to the environment and human health.Here we describe the design and implementation of an engineered Escherichia coli capable of degrading tetracycline(Tc)-one of the commonly used antibiotics once on humans and now on poultry,cattle and fisheries.A Tcdegrading enzyme,TetX,from the obligate anaerobe Bacteroides fragilis was cloned and recombinantly expressed in E.coli and fully characterized,including its Km and kcat value.We quantitatively evaluated its activity both in vitro and in vivo by UVeVis spectrometer and LC-MS.Moreover,we used a tetracycline inducible amplification circuit including T7 RNA polymerase and its specific promoter PT7 to enhance the expression level of TetX,and studied the dose-response of TetX under different inducer concentrations.Since the deployment of genetically modified organisms(GMOs)outside laboratory brings about safety concerns,it is necessary to explore the possibility of integrating a kill-switch.Toxin-Antitoxin(TA)systems were used to construct a mutually dependent host-plasmid platform and biocontainment systems in various academic and industrious situations.We selected nine TA systems from various bacteria strains and measured the toxicity of toxins(T)and the detoxifying activity of cognate antitoxins(A)to validate their potential to be used to build a kill-switch.These results prove the possibility of using engineered microorganisms to tackle antibiotic residues in environment efficiently and safely.

Run-and-Tumble Dynamics and Mechanotaxis Discovered in Microglial Migration

Microglia are resident macrophage cells in the central nervous system that search for pathogens or abnormal neural activities and migrate to resolve the issues.The effective search and targeted motion of macrophages mean dearly to maintaining a healthy brain,yet little is known about their migration dynamics.In this work,we study microglial motion with and without the presence of external mechanostimuli.We discover that the cells are promptly attracted by the applied forces(i.e.,mechanotaxis),which is a tactic behavior as yet unconfirmed in microglia.Meanwhile,in both the explorative and the targeted migration,microglia display dynamics that is strikingly analogous to bacterial run-and-tumble motion.A closer examination reveals that microglial run-and-tumble is more sophisticated,e.g.,they display a short-term memory when tumbling and rely on active steering during runs to achieve mechanotaxis,probably via the responses of mechanosensitive ion channels.These differences reflect the sharp contrast between microglia and bacteria cells(eukaryotes vs.prokaryotes)and their environments(compact tissue vs.fluid).Further analyses suggest that the reported migration dynamics has an optimal search efficiency and is shared among a subset of immune cells(human monocyte and macrophage).This work reveals a fruitful analogy between the locomotion of 2 remote systems and provides a framework for studying immune cells exploring complex environments.