微滴数字PCR和Super-ARMS检测晚期肺腺癌患者血浆循环肿瘤DNA表皮生长因子受体基因突变的临床价值研究

背景与目的晚期肺腺癌患者在选择靶向药物时需以肿瘤表皮生长因子受体(epidermal growth factor receptor, EGFR)基因突变类型作为依据,然而晚期肺腺癌肿瘤组织取材较难,有专家共识指出外周血可替代肿瘤组织作为检测标本。本文旨在探讨微滴数字聚合酶链反应法(droplet digital polymerase chain reaction, ddPCR)和超级扩增阻滞突变系统(super-amplification refractory mutation system, super-ARMS)这两种方法检测晚期肺腺癌患者外周血中血浆循环肿瘤脱氧核糖核酸(circulating tumor DNA, ctDNA)中EGFR基因突变的临床价值。方法收集2016年2月-2019年2月首都医科大学附属北京胸科医院确诊的初治晚期肺腺癌共119例纳入研究,比较ddPCR和Super-ARMS技术检测血浆ctDNA EGFR基因突变的敏感度、特异度。部分EGFR基因经典突变阳性患者接受一线EGFR酪氨酸激酶抑制剂(EGFR tyrosine kinase inhibitors, EGFR-TKI)口服治疗,将患者按检测结果分亚组,组1为ddPCR及Super-ARMS检测EGFR基因突变结果均为阳性,21例。组2为ddPCR及Super-ARMS检测EGFR基因突变结果均为阴性,16例。组3为ddPCR检测结果为阳性而Super-ARMS检测结果为阴性,5例。组4为ddPCR检测结果为阴性而Super-ARMS检测结果阳性,因组4患者个数为0,不纳入统计。以客观缓解率(objective response rate, ORR)及疾病控制率(disease control rate, DCR)评估近期疗效,并用生存分析比较组间无进展生存时间(progression-free survival, PFS)以评估远期疗效。结果 119例晚期肺腺癌组织样本中,共检测到58例(48.7%)EGFR基因突变。ddPCR技术检测与肿瘤组织EGFR基因突变结果的符合率为82.4%(Kappa=0.647, P<0.001),灵敏度为74.1%,特异度为90.2%。而Super-ARMS检测与组织检测的符合度为71.4%,灵敏度仅为58.6%,特异度为83.6%。组3的ORR与DCR值低于组1、2,但组间ORR相比均无统计学意义(P>0.05)。生存分析显示,三组患者PFS比较,差异无统计学意义(χ~2=2.221, P=0.329)。结论 ddPCR作为一种高敏感度及特异度的液体基因检测方法,可以作为检测晚期肺腺癌患者血浆ctDNA EGFR基因突变的一种较为可靠的方法。血浆基因检测结果同样可作为EGFR-TKIs药物对患者的疗效预测的依据。

新辅助免疫治疗联合化疗在可手术的非小细胞肺癌的初步疗效评估

背景与目的初步研究证实新辅助免疫联合化疗对可手术非小细胞肺癌近期疗效显著,但国内相关临床试验较少。本研究回顾性分析应用新辅助免疫治疗联合化疗的可手术Ⅰb期-Ⅲb期非小细胞肺癌的临床病理资料,初步评估新辅助免疫治疗联合化疗的疗效及安全性。方法回顾性分析2019年11月-2020年12月期间于首都医科大学附属北京胸科医院胸外科治疗的临床分期Ⅰb期-Ⅲb期的非小细胞肺癌患者20例,术前应用免疫联合化疗新辅助治疗,根据影像学和病理学方法分别评估疗效。结果全组患者新辅助治疗后影像学评估疗效,客观有效率(objective responserate,ORR)为85.0%(完全缓解4例,部分缓解13例),疾病稳定1例(5.0%),疾病进展2例(10.0%)。其中17例后续接受手术治疗,16例达到R0(no residual tumor)切除,1例R1(microscopic residual tumor)切除。术后病理评估:主要病理缓解率(major pathologic response,MPR)为47.1%(8/17),其中完全病理缓解率(complete pathologic response,CPR)为29.4%(5/17)。主要不良反应:免疫相关性肺炎(Ⅳ级)1例,Ⅲ级及以上血液学毒性9例(45.0%)。结论新辅助免疫联合化疗对于可手术的非小细胞肺癌近期疗效显著,具有一定的安全性及有效性。但新辅助免疫联合化疗的远期疗效、最佳周期数以及理想预测免疫治疗效果的标记物仍有待研究。

驱动基因阳性且PD-L1高表达的非小细胞肺癌患者病理特征及靶向治疗疗效评估的真实世界研究

背景与目的驱动基因突变阳性患者行靶向治疗,驱动基因阴性但程序性死亡配体1(programmed death-ligand 1,PD-L1)高表达患者行免疫抑制剂治疗,是晚期非小细胞肺癌(non-small cell lung cancer,NSCLC)患者一线治疗的首选,但对于驱动基因阳性且PD-L1高表达患者的治疗选择仍值得探究。方法以315例NSCLC患者为研究对象,分析驱动基因阳性且PD-L1高表达患者的临床病理特征及靶向治疗疗效。结果本研究纳入的315例NSCLC患者中,驱动基因突变总阳性率为62.2%,PD-L1高表达率(≥50.0%)为11.2%,驱动基因阳性且PD-L1高表达的患者比例为10.7%。其中表皮生长因子受体(epidermal growth factor receptor,EGFR)突变、KRAS突变、ALK融合、BRAF突变和MET 14外显子跳跃突变患者中均有PD-L1高表达,比例分别为7.8%(11/141)、18.2%(4/22)、23.1%(3/13)、50.0%(2/4)和100.0%(1/1)。EGFR突变且PD-L1高表达患者主要为IV期肺腺癌患者,KRAS突变且PD-L1高表达患者主要为有吸烟史的患者。其中详细跟踪了两例分别为ALK融合阳性且PD-L1高表达(90.0%)和EGFR L858R突变且PD-L1高表达(70.0%)患者的靶向治疗全过程,两例患者总生存期分别仅为5个月和2个月。结论NSCLC患者各驱动基因突变与PD-L1高表达共存的比例和临床病理特征有较大差异。发生敏感突变且PD-L1高表达的患者靶向治疗疗效和预后可能更差。

The RNA-binding protein Musashi2 governs osteoblast-adipocyte lineage commitment by suppressing PPARγsignaling

Osteoporosis caused by aging is characterized by reduced bone mass and accumulated adipocytes in the bone marrow cavity. How the balance between osteoblastogenesis and adipogenesis from bone marrow mesenchymal stem cells(BMSCs) is lost upon aging is still unclear. Here, we found that the RNA-binding protein Musashi2(Msi2) regulates BMSC lineage commitment. Msi2 is commonly enriched in stem cells and tumor cells. We found that its expression was downregulated during adipogenic differentiation and upregulated during osteogenic differentiation of BMSCs. Msi2 knockout mice exhibited decreased bone mass with substantial accumulation of marrow adipocytes, similar to aging-induced osteoporosis. Depletion of Msi2 in BMSCs led to increased adipocyte commitment. Transcriptional profiling analysis revealed that Msi2 deficiency led to increased PPARγ signaling.RNA-interacting protein immunoprecipitation assays demonstrated that Msi2 could inhibit the translation of the key adipogenic factor Cebpα, thereby inhibiting PPAR signaling. Furthermore, the expression of Msi2 decreased significantly during the aging process of mice, indicating that decreased Msi2 function during aging contributes to abnormal accumulation of adipocytes in bone marrow and osteoporosis. Thus, our results provide a putative biochemical mechanism for aging-related osteoporosis, suggesting that modulating Msi2 function may benefit the treatment of bone aging.

Coexistence of Quasi-two-dimensional Superconductivity and Tunable Kondo Lattice in a van der Waals Superconductor

Realization of Kondo lattice in superconducting van der Waals materials not only provides a unique opportunity for tuning the Kondo lattice behavior by electrical gating or intercalation,but also is helpful for further understanding the heavy fermion superconductivity.Here we report a low-temperature and vector-magneticfield scanning tunneling microscopy and spectroscopy study on a superconducting compound(4Hb-TaS_(2))with alternate stacking of 1T-TaS_(2)and 1H-TaS_(2)layers.We observe the quasi-two-dimensional superconductivity in the 1H-TaS_(2)layer with anisotropic response to the in-plane and out-of-plane magnetic fields.In the 1T-TaS_(2)layer,we detect the Kondo resonance peak that results from the Kondo screening of the unpaired electrons in the Star-of-David clusters.We also find that the intensity of the Kondo resonance peak is sensitive to its relative position with the Fermi level,and it can be significantly enhanced when it is further shifted towards the Fermi level by evaporating Pb atoms onto the 1T-TaS_(2)surface.Our results not only are important for fully understanding the electronic properties of 4Hb-TaS_(2),but also pave the way for creating tunable Kondo lattice in the superconducting van der Waals materials.

Evidence for Magnetic Fractional Excitations in a Kitaev Quantum-Spin-Liquid Candidate α-RuCl_(3)

It is known that α-RuCl_(3) has been studied extensively because of its proximity to the Kitaev quantum-spin-liquid(QSL)phase and the possibility of approaching it by tuning the competing interactions.Here we present the first polarized inelastic neutron scattering study on α-RuCl_(3) single crystals to explore the scattering continuum around the Γ point at the Brillouin zone center,which was hypothesized to be resulting from the Kitaev QSL state but without concrete evidence.With polarization analyses,we find that,while the spin-wave excitations around the Γ point vanish above the transition temperature T_(N),the pure magnetic continuous excitations around the Γ point are robust against temperature.Furthermore,by calculating the dynamical spin-spin correlation function using the cluster perturbation theory,we derive magnetic dispersion spectra based on the K-Γ model,which involves with a ferromagnetic Kitaev interaction of −7.2 meV and an off-diagonal interaction of 5.6 meV.We find this model can reproduce not only the spin-wave excitation spectra around the Γ point,but also the non-spin-wave continuous magnetic excitations around the Γ point.These results provide evidence for the existence of fractional excitations around the Γ point originating from the Kitaev QSL state,and further support the validity of the K-Γ model as the effective minimal spin model to describe α-RuCl_(3).

Quantum Oscillations in Noncentrosymmetric Weyl Semimetal SmAlSi

As a new type of quantum state of matter hosting low energy relativistic quasiparticles,Weyl semimetals(WSMs)have attracted significant attention for scientific community and potential quantum device applications.In this study,we present a comprehensive investigation of the structural,magnetic,and transport properties of noncentrosymmetric RAl Si(R=Sm,Ce),which have been predicted to be new magnetic WSM candidates.Both samples exhibit nonsaturated magnetoresistance,with about 900%and 80%for Sm Al Si and Ce Al Si,respectively,at temperature of 1.8 K and magnetic field of 9 T.The carrier densities of Sm Al Si and Ce Al Si exhibit remarkable change around magnetic transition temperatures,signifying that the electronic states are sensitive to the magnetic ordering of rare-earth elements.At low temperatures,Sm Al Si reveals prominent Shubnikov–de Haas oscillations associated with the nontrivial Berry phase.High-pressure experiments demonstrate that the magnetic order is robust and survival under high pressure.Our results would yield valuable insights into WSM physics and potentials in applications to next-generation spintronic devices in the RAl Si(R=Sm,Ce)family.

Neutron Spectroscopy Evidence for a Possible Magnetic-Field-Induced Gapless Quantum-Spin-Liquid Phase in a Kitaev Materialα-RuCl3

As one of the most promising Kitaev quantum-spin-liquid(QSL)candidates,α-RuCl_(3)has received a great deal of attention.However,its ground state exhibits a long-range zigzag magnetic order,which defies the QSL phase.Nevertheless,the magnetic order is fragile and can be completely suppressed by applying an external magnetic field.Here,we explore the evolution of magnetic excitations ofα-RuCl;under an in-plane magnetic field,by carrying out inelastic neutron scattering measurements on high-quality single crystals.Under zero field,there exist spin-wave excitations near the M point and a continuum near theΓpoint,which are believed to be associated with the zigzag magnetic order and fractional excitations of the Kitaev QSL state,respectively.By increasing the magnetic field,the spin-wave excitations gradually give way to the continuous excitations.On the verge of the critical fieldμ_(0)H_(c)=7.5 T,the former ones vanish and only the latter ones are left,indicating the emergence of a pure QSL state.By further increasing the field strength,the excitations near theΓpoint become more intense.By following the gap evolution of the excitations near theΓpoint,we are able to establish a phase diagram composed of three interesting phases,including a gapped zigzag order phase at low fields,possibly gapless QSL phase nearμ;H;,and gapped partially polarized phase at high fields.These results demonstrate that an in-plane magnetic field can driveα-RuCl;into a long-sought QSL state near the critical field.

Observation of a Ubiquitous(π,π)-Type Nematic Superconducting Order in the Whole Superconducting Dome of Ultra-Thin BaFe_(2-x)Ni_(x)As_(2) Single Crystals

In iron-based superconductors,the(0,π) or(π,0) nematicity,which describes an electronic anisotropy with a fourfold symmetry breaking,is well established and believed to be important for understanding the superconducting mechanism.However,how exactly such a nematic order observed in the normal state can be related to the superconducting pairing is still elusive.Here,by performing angular-dependent in-plane magnetoresistivity using ultra-thin flakes in the steep superconducting transition region,we unveil a nematic superconducting order along the(π,π) direction in electron-doped BaFe_(2-x)Ni_(x)As_(2) from under-doped to heavily overdoped regimes with x=0.065- 0.18.It shows superconducting gap maxima along the(π,π) direction rotated by 45° from the nematicity along(0, π) or(π,0) direction observed in the normal state.A similar(π,π)-type nematicity is also observed in the under-doped and optimally doped hole-type Ba1-yKyFe2 As_(2),with y=0.2-0.5.These results suggest that the(π,π) nematic superconducting order is a universal feature that needs to be taken into account in the superconducting pairing mechanism in iron-based superconductors.

Recent progress on magnetic-field studies on quantum-spin-liquid candidates

Quantum spin liquids（QSLs） represent a novel state of matter in which quantum fluctuations prevent the conventional magnetic order from being established, and the spins remain disordered even at zero temperature. There have been many theoretical developments proposing various QSL states. On the other hand, experimental movement was relatively slow largely due to limitations on the candidate materials and difficulties in the measurements. In recent years, the experimental progress has been accelerated. In this topical review, we give a brief summary of experiments on the QSL candidates under magnetic fields. We arrange our discussions by two categories： i） Geometrically-frustrated systems, including triangularlattice compounds YbMgGaO4 and YbZnGaO4, κ-（BEDT-TTF）2 Cu2（CN）3, and EtMe3 Sb[Pd（dmit）2]2, and the kagom′e system ZnCu3（OH）6 Cl2; ii） the Kitaev material α-RuCl3. Among these, we will pay special attention to α-RuCl3, which has been intensively studied by ours and other groups recently. We will present evidence that both supports and rejects the QSL ground state for these materials, based on which we give several perspectives to stimulate further research activities.

Inducing piezoelectricity in distorted rutile TiO_(2)for enhanced tetracycline hydrochloride degradation through photopiezocatalysis

Various material design strategies have been developed to enhance photocatalytic performance of TiO_(2).However,no report is available on applications of the photopiezocatalysis strategy on TiO_(2)due to its lack of piezoelectricity.Here we developed a low-temperature molten salt etching process to create rutile TiO_(2)nanoparticles by etching[MgO_(6)]octahedrons away from MgTiO_(3)by molten NH_(4)Cl,during which a lattice distortion occurred in TiO_(2).The lattice distortion broke the structure symmetry of rutile TiO_(2)and subsequently endowed these rutile TiO_(2)nanoparticles with an unusual piezoelectric response with the maximum effective piezoelectric coefficient(d_(33))of~41.6 pm/V,which had not previously been found in TiO_(2)photocatalysts.Thus,the photopiezocatalysis strategy was applied for the first time to enhance the photocatalytic performance of these TiO_(2)nanoparticles.The creation of lattice distortion to induce piezoelectricity could be extended to other photocatalysts that the photopiezocatalysis strategy has not been applied to and may generate novel functionalities for various technical applications.

Prognostic role of C-reactive protein to albumin ratio in lung cancer:An updated systematic review and meta-analysis

Background: C-reactive protein to albumin ratio(CRP/Alb ratio,CAR)has been suggested as a potential prognostic biomarker in lung cancer.This updated systematic review and meta-analysis aimed to assess the association between CAR and lung cancer prognosis in current literature.Methods: A systematic search of databases was conducted to identify relevant studies published up to April 2023.Pooled hazard ratios(HRs)and 95%confidence intervals(CIs)were calculated to assess the association between CAR and overall survival(OS)and progression-free survival(PFS)and recurrence-free survival(RF)in lung cancer patients.Results: This meta-analysis includes 16 studies with a total of 5337 patients,indicating a significant association between higher CAR and poorer OS,PFS,and RFS in lung cancer patients,with a pooled HR of 1.78(95%CI=1.60-1.99),1.57(95%CI=1.36-1.80),and 1.97(95%CI=1.40-2.77),respectively.Conclusions: This updated meta-analysis provides evidence for the potential prognostic role of CAR in lung cancer,suggesting its utility as an effective and noninvasive biomarker for identifying high-risk patients and informing treatment decisions in a cost-effective manner.However,further large-scale studies will be necessary to establish the optimal cut-off value for CAR in lung cancer and confirm the present findings.

Sex differences in eye movements and neural oscillations during mental rotation in virtual reality

Virtual reality(VR)has been a promising tool for developing visuospatial tasks.Among visuospatial tasks,mental rotation tasks are widely used in the assessment of visuospatial ability.Males have a distinct advantage in mental rotation ability compared to females,yet it is generally produced by investigations based on two-dimensional(2D)images on a computer screen.Sex differences in mental rotation tasks with three-dimensional(3D)objects in VR were not fully investigated.It is unclear whether the male's advantages in 2D mental rotation tasks are weakened in 3D tasks.The aim of this study was to provide new insights into the understanding of sex differences in mental rotation tasks presented in VR.Here,we developed a VR mental rotation task(VR-MRT)using 3D objects presented by a head-mounted display(HMD)and used VR-based eye tracking and electroencephalography(EEG)to examine eye movements and neural oscillations for males and females.Our results showed that females preferred a piecemeal strategy compared to males,suggesting a significant sex difference in visual strategy.More importantly,we found no significant sex differences in alpha-band and beta-band oscillations related to rotation processes of VR-MRT.These findings indicated that sex differences in the VR-MRT were mainly attributed to the selection of visual strategy rather than the rotation processes.The study helps to comprehensively understand the dominant factors contributing to the sex differences in the VR-MRT.

From the teapot effect to tap-triggered self-wetting: a 3D self-driving sieve for whole blood filtration

Achieving passive microparticle filtration with micropore membranes is challenging due to the capillary pinning effect of the membranes.Inspired by the teapot effect that occurs when liquid(tea)is poured from a teapot spout,we proposed a tap-triggered self-wetting strategy and utilized the method with a 3D sieve to flter rare cells.First,a 3D-printed polymer tap-trigger microstructure was implemented.As a result,the 3μm micropore membrane gating threshold(the pressure needed to open the micropores)was lowered from above 3000 to 80 Pa by the tap-trigger microstructure that facilated the liquid leakage and spreading to self-wet more membrane area in a positive feedback loop.Then,we implemented a 3D cone-shaped cell sieve with tap-trigger microstructures.Driven by gravity,the sieve performed at a high throughput above 20 mL/min(DPBS),while the micropore size and porosity were 3μm and 14.1%,respectively.We further filtered leukocytes from whole blood samples with the proposed new 3D sieve,and the method was compared with the traditional method of leukocyte isolation by chemically removing red blood cells.The device exhibited comparable leukocyte purity but a higher platelet removal rate and lower leukocyte simulation level,facilitating downstream single-cell analysis.The key results indicated that the tap-triggered self-wetting strategy could significantly improve the performance of passive microparticle filtration.

间歇性外斜视患者知觉眼位和主观斜视角的比较

目的:通过和同视机主观斜视角比较,了解间歇性外斜视患者知觉眼位的情况和意义。方法:系列病例研究。对2017年2-8月在北京同仁医院的间歇性外斜视患者分别用同视机检测其主观斜视角和用基于计算机平台的视感知觉检查方法检测其知觉眼位,将同时具备以上2项检测结果的患者作为研究对象。对二者水平方向眼位进行线性相关分析;统计同视机主观斜视角在垂直方向眼位偏斜的检出率,对同视机主观斜视角未检出垂直偏斜者分析其垂直知觉眼位的分布情况;对水平和垂直知觉眼位进行线性相关和回归分析。结果:共有120例间歇性外斜视患者被纳入研究。在水平方向,主观斜视角为(-8.1±5.3)°,知觉眼位偏移值为(332±233)像素,同视机主观斜视角越向外偏移,水平方向的知觉眼位偏移越大(r=-0.383,P<0.001)。在垂直方向,3例(2.5%)同视机检测到眼位偏斜,117例未检测出垂直眼位偏斜者中有113例(94.2%)可检测出不同程度的知觉眼位偏差,为(22±29)像素,其中67.5%(81/120)≤26像素(垂直眼位偏斜在0.5°以内),有82.5%(99/120)≤53像素(垂直眼位偏斜在1°以内)。120例患者垂直方向知觉眼位偏移为(24±32)像素,它与水平方向知觉眼位偏移呈线性相关关系(r=0.373,P<0.001),线性回归方程为垂直知觉眼位偏移=6.403+0.052×水平知觉眼位偏移(F=19.093,P<0.001)。结论:同视机主观斜视角与知觉眼位偏移均能反映间歇性外斜视患者双眼分视状态下水平方向的眼位偏斜状态;知觉眼位检查在垂直方向的眼位偏斜检出率明显高于同视机;垂直方向的知觉眼位偏斜随着水平方向知觉眼位偏斜的增加而增大。

视感知觉检查系统对共同性外斜视术后立体视功能重建的相关预测因素

目的:引入视感知觉可塑性评分检查训练系统,评价该检测方法在临床应用中预测共同性外斜视术后立体视恢复状况的准确度以及灵敏度和特异度。方法:前瞻性临床研究。连续收集2017年1─9月在北京同仁医院诊断为共同性外斜视且进行手术治疗的患者136例,在术后1周接受视感知觉可塑性评分检查。采用秩相关分析手术年龄、病程时长、术前斜视角度、术后1周斜视角度等因素与可塑性评分相关性。所有患者均从术后1周开始进行视感知觉训练,分别于术后1、3、6个月进行远、近立体视功能检测,制作ROC曲线,评价可塑性评分对术后不同时间点远、近立体视功能恢复预测的准确度及灵敏度和特异度。采用Delong test将可塑性评分以及传统临床指标对半年立体视功能的恢复状况的预测效能进行比较。结果:间歇性外斜视患者109例(80.2%),恒定性外斜视27例(19.9%)。可塑性评分分别与年龄、术前斜视度、斜视病程、外斜视类型、术后1周斜视度相关(r=-0.3、-0.2、-0.3、0.4、-0.3,均P<0.05)。可塑性评分在术后半年内不同时间点对立体视功能均具有预测能力,其中对术后6个月远、近立体视功能恢复正常均具有中等程度的预测意义,曲线下面积(AUC)均>0.7,P<0.001。传统临床指标中,术前近立体视功能对术后半年近立体视功能有较低的预测能力(AUC=0.63<0.7,P=0.009);术前看远斜视角度对术后6个月远、近立体视功能能否完全恢复正常具有较低的预测能力(AUC=0.66<0.7,P=0.02),但这些指标与可塑性评分的预测能力相比,差异无统计学意义(Z=1.2、1.4,P>0.05)。结论:视感知觉检查训练系统中,可塑性评分可以有效地预测共同性外斜视患者术后远、近立体视功能的恢复状况,为术后患者制定进一步的诊疗策略提供依据。

Problems and solutions in the protection of historical urban areas

Historical urban areas are the memory of a city, and the overall Landscape they constitute dispLays the typical scene of a city in a certain historical period. Thus, they are of value for protection. The current study gives an overview on the origin and protection of historical urban areas in the world. Moreover, the study also focuses on the principles, methods, and current problems in the protection of historical urban areas under the guidance of related taws and regulations in China. FinaLLy, some effective measures to protect historicat urban areas are suggested.

Turning ZrTe_5 into a semiconductor through atom intercalation

In this study we successfully intercalated potassium(K) atoms into single ZrTe_5 crystals by liquid ammonia method, and found a semimetal-to-semiconductor transition at low temperatures in K-intercalated ZrTe_5. As the K concentration increased, the resistance anomalous peak was gradually suppressed until finally disappearing. Whilst, the corresponding Hall resistance measurements consistently showed a sign reversal. The semimetal-to-semiconductor transition can be attributed to a lattice expansion induced by atom intercalation, leading to a larger energy band gap.

Highly crystalline ReSe2 atomic layers synthesized by chemical vapor transport

Two-dimensional (2D) anisotropic rhenium diselenide (ReSe2) has attracted lots ofattention due to its promising applications in electronics and optoelectronics. However,controlled synthesis of high quality ultrathin ReSe2 remains as a challenge.Here we developed an approach for synthesizing high quality 2D ReSe2 flakes witha thickness down to monolayer by chemical vapor transport (CVT) through carefullytuning the growth kinetics. The atomic structures and anisotropy of theobtained ReSe2 flakes were intensively characterized with scanning transmissionelectron microscope and angle-resolved polarized Raman spectroscopy. Fieldeffecttransistors fabricated on the CVT-grown ReSe2 flakes showed n-typesemiconducting behavior with an on/off current ratio of 105 and a mobility up to
5 cm2 V−1 s−1, which is comparable to mechanically exfoliated flakes and isobvious higher than the samples synthesized with other approaches. This study notonly make high quality 2D ReSe2 easily accessible for both fundamental and applicationexplorations but also sheds new lights on the chemical synthesis of otheranisotropic 2D materials.

Promotional effect of silica on the combustion of nano-sized aluminum powder in carbon dioxide

This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.