Highly selective growth of(6,5)single-walled carbon nanotubes from sigma phase alloy catalyst

The chirality structure of a single-walled carbon nanotube(SWNT)strongly depends on the composition of catalyst used in the chemical vapor deposition process.In this study,we develop a porous magnesia supported manganese-rhenium(MnRe/MgO)catalyst for chirality-selective synthesis of SWNTs.Detailed characterizations reveal that(6,5)tubes with a selectivity higher than 70%are grown from the Re-rich MnRe/MgO catalyst.By comparing the SWNT growth results with those of monometallic Mn or Re,the formation of sigma phase,an intermetallic compound occurring in transition-metal alloy systems,is revealed to be crucial for the dominant synthesis of(6,5)SWNTs.This work not only extends the application of sigma phase alloy for catalytic synthesis of SWNTs,but also sheds lights on the growth of SWNTs with a high chirality selectivity.

Unlocking the potential of ultra-thin two-dimensional antimony materials:Selective growth and carbon coating for efficient potassium-ion storage

Antimony-based anodes have attracted wide attention in potassium-ion batteries due to their high theoretical specific capacities(∼660 mA h g^(-1))and suitable voltage platforms.However,severe capacity fading caused by huge volume change and limited ion transportation hinders their practical applications.Recently,strategies for controlling the morphologies of Sb-based materials to improve the electrochemical performances have been proposed.Among these,the two-dimensional Sb(2D-Sb)materials present excellent properties due to shorted ion immigration paths and enhanced ion diffusion.Nevertheless,the synthetic methods are usually tedious,and even the mechanism of these strategies remains elusive,especially how to obtain large-scale 2D-Sb materials.Herein,a novel strategy to synthesize 2D-Sb material using a straightforward solvothermal method without the requirement of a complex nanostructure design is provided.This method leverages the selective adsorption of aldehyde groups in furfural to induce crystal growth,while concurrently reducing and coating a nitrogen-doped carbon layer.Compared to the reported methods,it is simpler,more efficient,and conducive to the production of composite nanosheets with uniform thickness(3–4 nm).The 2D-Sb@NC nanosheet anode delivers an extremely high capacity of 504.5 mA h g^(-1) at current densities of 100 mA g^(-1) and remains stable for more than 200 cycles.Through characterizations and molecular dynamic simulations,how potassium storage kinetics between 2D Sb-based materials and bulk Sb-based materials are explored,and detailed explanations are provided.These findings offer novel insights into the development of durable 2D alloy-based anodes for next-generation potassium-ion batteries.

Selective growth of wide band gap atomically thin Sb2O3 inorganic molecular crystal on WS2

Heterostructures combined by different individual two-dimensional(2D)materials are essential building blocks to realize unique electronic,optoelectronic properties and multifunctional applications.To date,the direct growth of 2D/2D atomic van der Waals heterostructures(vdWHs)have been extensively investigated.However,the heterostructures from 2D inorganic molecular crystals and atomic crystals have been rarely reported.Here we report two-step direct epitaxial growth of the inorganic molecular-atomic Sb2O3/WS2 vdWHs.The thickness of Sb2O3 nanosheets on WS2 nanosheets can be tuned by variable growth temperatures.Oriented growth behavior of Sb2O3 on WS2 was determined through statistics.Optical images,Raman spectra,Raman mappings and selected-area electron diffraction(SAED),etc.,reveal that Sb2O3/WS2 heterostructures are vertically stacked with high crystal quality.Electrical transport measurements demonstrate that the heterotransistors based on the heterostructures possess high current on/off ratio of 5 × 10^5,obvious gate-tunable and current rectification output characteristics.Optoelectronic characterizations show that the heterostructures have a clear photoresponse with high responsivity of 16.4 AW.The growth of vdWHs from 2D inorganic molecular-atomic crystals may open up new opportunities in 2D functional electronics and optoelectronics.

Synthesis of quaternary 8-(1-acylethene-1-yl)-13-methylcoptisine chlorides and their selective growth inhibitory activity between human cancer cell lines and normal intestinal epithelial cell-6

In this paper, quaternary 8-(1-acylethene-1-yl)-13-methylcoptisine chlorides targeting thioredoxin reductases(TrxRs) were designed to test the growth inhibitory activity against human cancer cell lines and the effect on viability of the normal intestinal epithelial cell-6(IEC-6) in vitro and to evaluate structure-activity relationship(SAR). The introduced α, β-unsaturated ketone groups at C-8 consisting of n-alkanoyls possessing five to ten carbons or aroyls or cyclohexylcarbonyl increased the tested activity against the target cancer cell lines. By and large, this type of improvement was increasingly graced by the elongation of the aliphatic chain of the n-alkanoyls in the range of less than ten carbon atoms. The relatively more polar 1-acylethene-1-yls displayed no effect on improving the activity. All the explored aroyls showed significant effect on improving the activity of the target compounds against the tested cancer cell lines with no SAR being observed. The findings of this study suggested that oil/water partition coefficient of the test compounds was one of the key factors impacting the target activity against the tested cancer cell lines. At the concentration of 10 μmol/L, except for the compounds with n-alkanoyls possessing seven or more carbons or with α-naphthoyl, none of the other compounds displayed obvious cytotoxicity on normal IEC-6 cell when co-incubated. The survival rate of IEC-6 cell ranged from 75% to 100% for the noncytotoxic compounds.

Influence of adatom migration on wrinkling morphologies of AlGaN/GaN micro-pyramids grown by selective MOVPE

Ga N micro-pyramids with AlGaN capping layer are grown by selective metal–organic–vapor phase epitaxy(MOVPE). Compared with bare Ga N micro-pyramids, AlGaN/Ga N micro-pyramids show wrinkling morphologies at the bottom of the structure. The formation of those special morphologies is associated with the spontaneously formed AlGaN polycrystalline particles on the dielectric mask, owing to the much higher bond energy of Al–N than that of Ga–N. When the sizes of the polycrystalline particles are larger than 50 nm, the uniform source supply behavior is disturbed, thereby leading to unsymmetrical surface morphology. Analysis reveals that the scale of surface wrinkling is related to the migration length of Ga adatoms along the AlGaN {1ī01} facet. The migration properties of Al and Ga further affect the distribution of Al composition along the sidewalls, characterized by the μ-PL measurement.

Selective Fetal Growth Restriction in Monochorionic Diamniotic Twins: Diagnosis and Management

Selective fetal growth restriction (sFGR) is a severe condition that complicates 10% to 15% of all monochorionic diamniotic (MCDA) twin pregnancies. Pregnancies complicated with sFGR are at high risk of intrauterine demise or adverse perinatal outcome for the twins. Three clinical types have been described according to the umbilical artery (UA) Doppler pattern observed in the smaller twin: type I, when the UA Doppler is normal;type II, when there is persistent absent or reversed end-diastolic blood flow in the UA Doppler;and type III, when there is intermittent absent and/or reversed end-diastolic blood flow in the UA Doppler. Clinical evolution and management options mainly depend on the type of sFGR. Type I is usually associated with a good prognosis and is managed conservatively. There is no consensus on the management of types II and III, but in earlier and more severe presentations, fetal interventions such as selective laser photocoagulation of placental anastomoses or selective fetal cord occlusion of the smaller twin may be considered. This review aims to provide updated information about the diagnosis, evaluation, follow-up, and management of sFGR in MCDA twin pregnancies.

High crystalline quality of SiGe fin fabrication with Si-rich composition area using replacement fin processing

A high crystalline quality of SiGe fin with an Si-rich composition area using the replacement fin processing is systematically demonstrated in this paper.The fin replacement process based on a standard FinFET process is developed.A width of less than 20-nm SiGe fin without obvious defect impact both in the direction across the fin and in the direction along the fin is verified by using the high angle annular dark field scanning transmission electron microscopy and the scanning moiréfringe imaging technique.Moreover,the SiGe composition is inhomogenous in the width of the fin.This is induced by the formation of 111 facets.Due to the atomic density of the 111 facets being higher,the epitaxial growth in the direction perpendicular to these facets is slower than in the direction perpendicular to 001.The Ge incorporation is then higher on the 111 facets than on the 001 facets.So,an Si-rich area is observed in the central area and on the bottom of SiGe fin.

Screwdriver-like Pd-Ag heterostructures formed via selective deposition of Ag on Pd nanowires as efficient photocatalysts for solvent-free aerobic oxidation of toluene

Heterostructured bimetal nanocrystals with a component having localized surface plasmon resonance(LSPR)property are promising photocatalysts for a series of reactions.In this work,kinetic products of Pd-Ag with a screwdriver-like heterostructure have been successfully fabricated via the selective epitaxial growth of Ag on Pd nanowires(NWs).It was confirmed that the deposition rate(Vdeposition)of Ag is much more sensitive to the temperature,compared to the surface diffusion rate(Vdiffusion)which can be effectively reduced by the binding of poly(vinylpyrrolidone)(PVP)molecules.Then the magnitude of Vdeposition/Vdiffusion has been well tailored for the formation of a kinetic growth environment.The interactions between the components of the as-prepared Pd-Ag heterostructures resulted in intensified LSPR effects.As a result,they gained better photocatalytic performance toward solvent free aerobic oxidation of toluene than Pd NWs,Ag NWs and the mixture of them.Additionally,the Pd-Ag heterostructured nanocrystals exhibited excellent catalytic stability for recycling.This work not only presents an idea for realizing kinetic growth but also supports that LSPR effect is a good tool for improving the photocatalytic activity.

The Proteome Landscape of Human Placentas for Monochorionic Twins with Selective Intrauterine Growth Restriction

In perinatal medicine,intrauterine growth restriction(IUGR)is one of the greatest challenges.The etiology of IUGR is multifactorial,but most cases are thought to arise from placental insufficiency.However,identifying the placental cause of IUGR can be difficult due to numerous confounding factors.Selective IUGR(sIUGR)would be a good model to investigate how impaired placentation affects fetal development,as the growth discordance between monochorionic twins cannot be explained by confounding genetic or maternal factors.Herein,we constructed and analyzed the placental proteomic profiles of IUGR twins and normal cotwins.Specifically,we identified a total of 5481 proteins,of which 233 were differentially expressed(57 up-regulated and 176 down-regulated)in IUGR twins.Bioinformatics analysis indicates that these differentially expressed proteins(DEPs)are mainly associated with cardiovascular system development and function,organismal survival,and organismal development.Notably,34 DEPs are significantly enriched in angiogenesis,and diminished placental angiogenesis in IUGR twins has been further elaborately confirmed.Moreover,we found decreased expression of metadherin(MTDH)in the placentas of IUGR twins and demonstrated that MTDH contributes to placental angiogenesis and fetal growth in vitro.Collectively,our findings reveal the comprehensive proteomic signatures of placentas for sIUGR twins,and the DEPs identified may provide in-depth insights into the pathogenesis of placental dysfunction and subsequent impaired fetal growth.

AlGaN/GaN high electron mobility transistors with selective area grown p-GaN gates

We report a selective area growth(SAG) method to define the p-GaN gate of AlGaN/GaN high electron mobility transistors(HEMTs) by metal-organic chemical vapor deposition.Compared with Schottky gate HEMTs,the SAG p-GaN gate HEMTs show more positive threshold voltage(V_(th)) and better gate control ability.The influence of Cp_2Mg flux of SAG p-GaN gate on the AlGaN/GaN HEMTs has also been studied.With the increasing Cp_2Mg from 0.16 μmol/min to 0.20 μmol/min,the V_(th) raises from-0.67 V to-0.37 V.The maximum transconductance of the SAG HEMT at a drain voltage of 10 V is 113.9 mS/mm while that value of the Schottky HEMT is 51.6 mS/mm.The SAG method paves a promising way for achieving p-GaN gate normally-off AlGaN/GaN HEMTs without dry etching damage.

Rational distribution of Ru nanodots on 2D Ti_(3−x)C_(2)T_(y)/g-C_(3)N_(4)heterostructures for boosted photocatalytic H_(2)evolution

Incorporating metal nanodots(NDs)into heterostructures for high charge separation and transfer capacities is one of the most effective strategies for improving their photocatalytic activities.However,controlling the space distribution of metal NDs for optimizing charge transport pathways remains a significant challenge,particularly in two-dimensional(2D)face-to-face heterostructures.Herein,we develop a simple targeted self-reduction strategy for selectively loading Ru NDs onto the Ti_(3−x)C_(2)T_(y)(TC)surface of 2D TC/g-C_(3)N_(4)(CN)heterojunction based on the reductive Ti vacancy defects creatively increased during the preparation of TC/CN by reducing calcination.Notably,the optimized Ru/TC/CN photocatalyst exhibits an outstanding H_(2)evolution rate of 3.21 mmol·g^(−1)·h^(−1)and a high apparent quantum efficiency of 30.9%at 380 nm,which is contributed by the unidirectional transfer of the photogenerated electrons from CN to Ru active sites(CN→TC→Ru)and the suppressed backflow of electrons from Ru sites to CN,as revealed by comprehensive characterizations and density functional theory(DFT)calculations.This work provides a novel strategy for synthesizing the highly efficient photocatalysts with a controllable charge transfer paths,which will boost the development of photocatalysis.

Complications of Monochorionic Diamniotic Twins: Stepwise Approach for Early Identification, Differential Diagnosis, and Clinical Management

One in three monochorionic twins may develop complications during pregnancy. Monochorionic twins, especially monochorionic diamniotic (MCDA), present specific problems caused by the presence of interfetal placental anastomoses. The first critical step in the management of MCDA twins is identification in the first trimester. Secondly, close follow-up every 2 weeks is mandatory to allow early diagnosis and timely treatment of twin-twin transfusion syndrome. Other potentially severe complications include selective fetal growth restriction, twin anemia polycythemia syndrome or single fetal death. Thirdly, a correct differential diagnosis is critical to establish the best therapy. This may represent a clinical challenge since MCDA twin complications often overlap. A simple diagnostic algorithm may be of great help to establish the right diagnosis and management option. In this review we summarize the main steps for the clinical follow-up, differential diagnosis, and targeted management of MCDA twins complications.

Gate length dependent transport properties of in-plane core-shell nanowires with raised contacts

Three-dimensional(3D)nanoscale crystal shaping has become essential for the precise design of advanced electronic and quantum devices based on electrically gated transport.In this context,Ⅲ-Ⅴ semiconductor-based nanowires with low electron effective mass and strong spin-orbit coupling are particularly investigated because of their exceptional quantum transport properties and the good electrostatic control they provide.Among the main challenges involved in the processing of these nanodevices are(i)the management of the gate stack which requires ex-situ passivation treatment to reduce the density of traps at the oxide/semiconductor interface,(ii)the ability to get good ohmic contacts for source and drain electrodes and(iii)the scalability and reliability of the process for the fabrication of complex architectures based on nanowire networks.In this paper,we show that selective area molecular beam epitaxy of in-plane InGaAs/InP core-shell nanowires with raised heavily doped source and drain contacts can address these different issues.Electrical characterization of the devices down to 4 K reveals the positive impact of the InP shell on the gate electrostatic control and effective electron mobility.Although comparable to the best reported values for In(Ga)As nanostructures grown on InP,this latter is severely reduced for sub-100 nm channel highlighting remaining issue to reach the ballistic regime.

Nonpolar Al_(x)Ga_(1−x)N/Al_(y)Ga_(1−y)N multiple quantum wells on GaN nanowire for UV emission

Nonpolar m-plane AlGaN offers the advantage of polarization-free multiple quantum wells(MQWs)for ultraviolet(UV)emission and can be achieved on the sidewalls of selective area grown GaN nanowires.We reveal that the growth of AlGaN on GaN nanowires by metal organic chemical vapor deposition(MOCVD)is driven by vapor-phase diffusion,and consequently puts a limit on the pitch of nanowire array due to shadowing effect.An insight into the difficulty of achieving metal-polar AlGaN nanowire by selective area growth(SAG)in MOCVD is also provided and can be attributed to the strong tendency to form pyramidal structure due to a very small growth rate of{1011}semipolar planes compared to(0001)c-plane.The nonpolar m-plane sidewalls of GaN nanowires obtained via SAG provides an excellent platform for growth of nonpolar AlGaN MQWs.UV emission from mplane Al_(x)Ga_(1−x)N/Al_(y)Ga_(1−y)N MQWs grown on sidewalls of dislocation-free GaN nanowire is demonstrated in the wavelength range of 318–343 nm.

The Controversies and Challenges in the Management of Twin Pregnancy: From the Perspective of International Federation of Gynecology and Obstetrics Guidelines

The rate of multiple pregnancy is increasing, mainly because of the widespread use of assisted reproduction techniques and families’ desire for twins. Twin pregnancy accounts for a higher risk of chromosomal abnormalities, structural malformations, and neonatal adverse events than singleton pregnancy. The presence of artery-vein anastomoses, unbalanced placenta sharing, and abnormal cord insertion in monochorionic twins is associated with twin complications such as twin-to-twin transfusion syndrome, selective intrauterine growth restriction, and twin anemia polycythemia sequence. Although many guidelines and studies have established and improved the processes about the antenatal surveillance and management of twin pregnancy, they also raise more controversies and challenges. This review aims to highlight the international consensus on the antenatal care of twin pregnancies and analyze the controversies and predicaments based on the published International Federation of Gynecology and Obstetrics guidelines and research.