含Benzo[a]azulene单元的锯齿状梯形共轭聚合物的表面在位合成

梯形共轭聚合物(CLPs)因其独特的光电性质而受到广泛关注。绝大多数CLPs是通过溶液方法合成的,但近年来,在超高真空环境中进行的表面原位合成策略逐渐崭露头角,成为CPL合成的新方法。表面原位合成方法能够克服传统溶液合成的限制,如随着聚合度增加而受限的溶解度和结构稳定性,从而实现复杂共轭结构的精确合成。Azulene衍生物是在表面合成非苯型CLPs的有吸引力的前体。与传统的只含六元环的CLPs相比,使用烷基取代的azulene作为前体分子,有望获得具有复杂骨架结构的CLPs,从而调控其电子性质,但目前很少有人探索这种策略。本文报道了3,3'-二溴-2,2’-二甲基-1,1’-联薁(DBMA)在Au(111)表面上的热化学反应。在室温的Au(111)衬底上,我们发现沉积的分子在重构表面的fcc(面心立方堆积)区域形成无定型的聚集体,并在100℃以下保持形貌不变。当退火温度高于150℃后,DBMA发生脱溴反应并与金原子络合形成具有复杂空间立体结构的2,2’-二甲基-1,1’-联薁有机金属聚合物,并展现出迥异的图像特征。随后在更高温度下退火,有机金属聚合物脱去金属原子并经历碳碳偶联反应。该过程伴随着甲基与相邻薁单元之间的分子内环化反应,形成了含有benzo[a]azulene单元的梯形共轭聚合物。有趣的是,我们发现当一侧甲基参与反应并在聚合物中形成六元环时,会显著地弯折聚合物链,使得另一侧甲基与薁单元之间的距离增加,并抑制预期的环化过程。我们通过键分辨扫描探针显微镜对反应过程中的相关结构进行了研究,发现反应结果与反应中间结构的应力关联紧密。我们的结果表明,烷基取代的azulene前体可应用于非苯型碳纳米结构的表面合成,并有望实现扩展的非苯型二维碳纳米结构。

Equivalent formulae of stress Green's functions for a constant slip rate on a triangular fault

We present an equivalent form of the expres- sions first obtained by Tada （Geophys J Int 164：653-669, 2006. doi： 10.1111/j. 1365-246X.2006.03868.x）, which rep- resents the transient stress response of an infinite, homo- geneous and isotropic medium to a constant slip rate on a triangular fault that continues perpetually after the slip onset. Our results are simpler than Tada＇s, and the corre- sponding codes have a higher running speed.

Synthetic seismograms for finite sources in spherically symmetric Earth using normal-mode summation

Normal-mode summation is the most rapidly used method in calculating synthetic seismograms. How- ever, normal-mode summation is mostly applied to point sources. For earthquakes triggered by faults extending for as long as several 100 km, the seismic waves are usually simulated by point source summation. In this paper, we attempt to follow a different route, i.e., directly calculate the excitation of each mode, and use normal-mode sum- mation to obtain the seismogram. Furthermore, we assume the finite source to be a ＂line source＂ and numerically calculate the transverse component of synthetic seismo- grams for vertical strike-slip faults. Finally, we analyze the features in the Love waves excited by finite faults.

Acetone sensors for non-invasive diagnosis of diabetes based on metal-oxide-semiconductor materials

In recent years, clinical studies have found that acetone concentration in exhaled breath can be taken as a characteristic marker of diabetes. Metal-oxide-semiconductor (MOS) materials are widely used in acetone gas sensors due to their low cost, high sensitivity, fast response/recovery time, and easy integration. This paper reviews recent progress in acetone sensors based on MOS materials for diabetes diagnosis. The methods of improving the performance of acetone sensor have been explored for comparison, especially in high humidity conditions. We summarize the current excellent methods of preparations of sensors based on MOSs and hope to provide some help for the progress of acetone sensors in the diagnosis of diabetes.

Dynamic rupture process of the 1999 Chi-Chi,Taiwan,earthquake

In this study, we preliminarily investigated the dynamic rupture process of the 1999 Chi-Chi, Taiwan, earthquake by using an extended boundary integral equation method, in which the effect of ground surface can be exactly included. Parameters for numerical modeling were carefully assigned based on previous studies. Numerical results indicated that, although many simplifications are assumed, such as the fault plane is planar and all heterogeneities are neglected, distribution of slip is still consistent roughly with the results of kinematic inversion, implying that for earthquakes in which ruptures run up directly to the ground surface, the dynamic processes are controlled by geometry of the fault to a great extent. By taking the common feature inferred by various kinematic inversion studies as a restriction, we found that the critical slip-weakening distance Dc should locate in a narrow region [60 cm, 70 cm], and supershear rupture might occur during this earthquake, if the initial shear stress before the mainshock is close to the local shear strength.

Analysis of the role of branching angle in the dynamic rupture process on a 3-D branching fault system

The fault branching phenomenon,which may heavily influence the patterns of rupture propagation in fault systems,is one of the geometric complexities of fault systems that is widely observed in nature.In this study,we investigate the effect of the branching angle on the rupture inclination and the interaction between branch planes in two-fork branching fault systems by numerical simulation and theoretical analysis based on Mohr’s circle.A friction law dependent on normal stress is used,and special attention is paid to studying how ruptures on the upper and lower branch planes affect the stress and rupture on each other separately.The results show that the two branch planes affect each other in different patterns and that the intensity of the effect changes with the branching angle.The rupture of the lower branch plane has a negative effect on the rupture of the upper branch plane in the case of a small branching angle but has almost no negative effect in the case of a large branching angle.The rupture of the upper branch plane,however,suppresses the rupture of the lower branch plane regardless of whether the branching angle is large or small.

Boundary integral equations for dynamic rupture propagation on vertical complex fault system in half-space:Theory

The boundary integral equation method （BIEM） is now widely used in numerical studies on earthquake rupture dynamics, and is proved to be a powerful tool to deal with problems on complex fault system. However, since this method heavily lies on the specific forms of Green＇s function and only the Green＇s function in full-space has a closed analytic expression, it is usually limited to a full-space medium. In this study, as a first step to extend this method to an arbitrary complex fault system in half-space, the boundary integral equations （BIEs） for dynamic strike-slip on vertical complex fault system in half-space are derived based on exact Green＇s function for isotropic and homogeneous half-space. Effect of the geometry of the complex fault system are dealt with carefully. Final BIEs is composed of two parts： contribution from full-space, which has been thoroughly investigated by Aochi and his co-workers by using the Green＇s function for full-space, and that from free surface, which is studied in detail in this study.

活体肝脏捐献者生命质量影响因素的系统综述

目的旨在对活体肝脏捐献者捐献后生命质量的影响因素进行梳理和归纳,为临床护理制订有针对性的干预措施提供参考依据。方法对PubMed、EMBASE、CINHAL、Web of Science和ProQuest数据库进行检索。检索时间为建库至2022年6月,纳入经过同行评审的英文文献,包括对捐献后活体肝脏捐献者生命质量影响因素进行分析的横断面研究或纵向研究。采用美国国立卫生研究院横断面研究和纵向研究质量评估工具(修订版)对纳入研究的方法学质量进行评价。结果共检索出6576篇文献,16篇符合纳入标准。将文献中影响活体肝脏捐献者生命质量的相关因素归纳为4类:社会人口学因素(性别、年龄、受教育程度、民族和婚姻状况)、捐献肝脏相关因素(捐献相关的住院时间或住院次数、受者结局、捐献后时长、捐献后并发症、捐献决定受支持情况、术前对个人健康担忧、捐献前存在捐献的矛盾心理、与受者关系)、健康状况相关因素(体质指数和捐献前有躯体症状)和心理社会因素(捐献前躯体和心理状态评分、家庭收入、焦虑、抑郁)。多数研究报道,老年、受者死亡、捐献肝脏后近期、捐献者经历术后并发症以及捐献者对自身健康的担忧是躯体功能的负面影响因素。女性捐献者、低教育水平、因捐献而住院时间长和/或住院次数多、受者预后不佳、捐献后近期、捐献肝脏前对自身健康担忧以及一级亲属和配偶捐献者是捐献后不良心理状态的负面预测因素。纳入研究中,仅有2篇文献考虑了社会功能的影响因素。结论活体肝脏捐献者的生命质量不仅受到捐献手术的影响,还包括心理和社会方面的因素。临床护理工作者可根据上述影响因素为捐献者制订有针对性的护理措施,以提高肝脏捐献者的生命质量。

Dynamic inversion of the rupture parameters on fault system with complex geometry:A GPU parallel genetic algorithm based on BIEM

In this study,we attempted to perform an earthquake source dynamic inversion to obtain dynamic parameters on fault system with complex geometry.The forward modeling of the spontaneous rupture process is carried out using a boundary integral equation method(BIEM)based on unstructured meshing,and the inversion method is implemented by a genetic algorithm based on a parallel acceleration of the GPU.The source model in this study is a branched fault,which is described by two physical parameters,the initial stress T0 and the critical slip-weakening distance Dc.We investigated the effect of the inherited parameters on the accuracy and convergence of the inversion simulation.Numerical results showed that if a set of parameters are assigned properly,the inversion of rupture parameters is accurate and converges fast.It is easy to converge to a local optimal solution during the inversion process if inappropriate inherited parameters are selected.Compared with T0,D。has better convergence and accuracy in.the inversion process.

Giant piezotronic effect in ferroelectric field effect transistor

The piezotronics effect utilizes a piezopotential to modulate and control current in piezo-semiconductors.Ferroelectric materials,as a type of piezoelectric materials,possess piezoelectric coefficients that are significantly larger than those found in conventional piezoelectric materials.Here,we propose a strain modulated ferroelectric field-effect transistor(St-FeFET)utilizing external strain instead of gate voltage to achieve ferroelectric modulation,which eliminates the need for gate voltage.By applying a very small strain(0.01%),the St-FeFET can achieve a maximum on-off current ratio of 1250%and realizes a gauge factor(GF)of 1.19×10^(6),which is much higher than that of conventional strain sensors.This work proposes a new method for realizing highly sensitive strain sensors and presents innovative approaches to the operation methods of ferroelectric field-effect transistors as well as potential applications for coupling of strain sensors and various devices across different fields.

On-Surface Synthesis of Electron-Deficient Bisanthene Tetraimide

Imide-based conjugated molecules have emerged as a highly promising class of building blocks for constructing n-type semiconducting materials with lowlying lowest unoccupied molecular orbitals and exceptional stability.Although imides,such as naphthalene diimides,perylene diimides and their lateral fused analogs,have been synthesized extensively,the design and synthesis of largerπ-extended molecules incorporating more than two imide groups are desirable but still very challenging.Herein,we report the synthesis of an unprecedented electron-deficient bisanthene tetraimide(ATI)containing a bisantheneconjugated core and four five-membered imide groups,which was successfully achieved via a combined approach of solution and on-surface synthesis.The chemical structures,electronic states,formation mechanism and aromaticity of ATI were systematically investigated by scanning tunneling microscopy,noncontact atomic force microscopy,scanning tunneling spectroscopy,and density functional theory calculations.

表面在位化学与液相化学反应的关联和差别

作为一门化学与物理交叉的新兴学科,表面在位化学(on-surface chemistry)自诞生以来一直处于表面科学的研究前沿.表面在位化学反应既依托于传统溶液反应,又与传统液相化学反应有着明显的区别.传统溶液反应中的诸多经验、理论在表面在位化学反应中依旧适用,很多经典的溶液反应也能在表面上得以实现.然而,利用表面限域效应可以引发一系列在传统溶液反应中难以实现的,具有高精度、高选择性的化学反应,这使得表面在位化学在功能性大分子设计、合成化学以及新材料制备中显示出十分诱人的潜能.本文总结了一些具有代表性的表面在位化学反应,通过比较其与传统溶液反应路径和产物上的差别,归纳了表面在位化学的特点,并对这种"新型"反应手段未来将会面临到的机遇与挑战做出展望.

Crystal structure of Cr_4AlB_4: A new MAB phase compound discovered in Cr-Al-B system

In this communication, the crystal structure of Cr_4AlB_4, a new MAB phase compound(where M is a transition metal, A is Al or Si, B is boron) discovered in Cr-Al-B system is reported. This new MAB phase was synthesized from a mixture of CrB and Al powders at 1000?C and its crystal structure was determined by a combination of X-ray diffraction, first-principles calculations and energy dispersive X-ray spectroscopy(EDS). Cr_4AlB_4 crystallizes in an orthorhombic structure with Immm space group. The lattice constants are a = 2.9343(6) ?, b = 18.8911(0) ?, c = 2.9733(7) ?, and the atomic positions are Cr1 at 4 g(0, 0.2936(5),0), Cr2 at 4 h(0.5, 0.5859(7), 0), Al at 2 b(0, 0.5, 0.5), B1 at 4 h(0, 0.3839(8), 0.5) and B2 at 4 g(0.5, 0.6646(2),0.5).

Theoretical prediction,synthesis,and crystal structure determination of new MAX phase compound V2SnC

Guided by the theoretical prediction,a new MAX phase V2SnC was synthesized experimentally for the first time by reaction of V,Sn,and C mixtures at 1000°C.The chemical composition and crystal structure of this new compound were identified by the cross-check combination of first-principles calculations,X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDS),and high resolution scanning transmission electron microscopy(HR-STEM).The stacking sequence of V2C and Sn layers results in a crystal structure of space group P63/mmc.The a-and c-lattice parameters,which were determined by the Rietveld analysis of powder XRD pattern,are 0.2981(0)nm and 1.3470(6)nm,respectively.The atomic positions are V at 4f(1/3,2/3,0.0776(5)),Sn at 2d(2/3,1/3,1/4),and C at 2a(0,0,0).A new set of XRD data of V2SnC was also obtained.Theoretical calculations suggest that this new compound is stable with negative formation energy and formation enthalpy,satisfied Born-Huang criteria of mechanical stability,and positive phonon branches over the Brillouin zone.It also has low shear deformation resistance c44(second-order elastic constant,cij)and shear modulus(G),positive Cauchy pressure,and low Pugh’s ratio(G/B=0.500<0.571),which is regarded as a quasi-ductile MAX phase.The mechanism underpinning the quasi-ductility is associated with the presence of a metallic bond.

First demonstration of possible two-dimensional MBene CrB derived from MAB phase Cr_2AlB_2

In this communication, the possibility for the preparation of two-dimensional MBene CrB from MAB phase Cr2AlB2 is demonstrated for the first time. Herein M is a transition metal, A is a group IIIAor IVA element and B is boron; MAB phases are layered transition metal ternary borides, MBene is used to emphasize the loss of A group element from the parent MAB phases and to highlight the 2 D nature. The possible 2 D CrB nano sheets are prepared by selectively etching out Al layers from Cr2AlB-2 by immersing the Cr2AlB2 powders in dilute HCl solution at room temperature. The as-prepared 2 D CrB nano sheets are examined using X-ray diffraction and scanning electron microscopy and energy dispersive X-ray spectroscopy（EDS）. In addition, different structure models are built to explain the observed phenomena.The discovery in this work opens a door to the synthesis of a large number of new 2 D MBenes from MAB phases.

(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B:A novel high-entropy monoboride with good electromagnetic interference shielding performance in K-band

A novel equimolar high-entropy(HE)transition metal monoboride,(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B,was designed and prepared in powder and bulk form by high temperature elemental reaction method and spark plasma sintering(SPS)method,respectively.XRD analysis shows that HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B possesses orthorhombic structure with Pnma space group.Through Rietveld refinement,the lattice parameters of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B are a=5.6675,b=2.9714,c=4.2209 and the theoretical density is 6.95 g/cm~3.The Vickers hardness and electrical conductivity of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B bulk with relative density of 90%is 12.3±0.5 GPa and 0.49±0.04×10~6 S/m,respectively.Due to high electrical conductivity,HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B bulk with 3.0 mm thickness displays superior EMI shielding performance in 18.0–26.5 GHz(K-band),and the average values of SET,SER,and SEAare 23.3 dB,13.9 dB,and 9.4 dB,respectively.The EMI shielding mechanism of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B mainly results from reflection.

Phase pure and well crystalline Cr2AlB2:A key precursor for two-dimensional CrB

Phase pure and well crystalline Cr2AlB2 powders are synthesized by heating the mixtures of CrB and Al powders at 900~℃.Cr2AlB2 exhibits nanolaminated morphology which transforms from flake-like crystallite to needle-like grain with the increase of holding time.The morphology-structure relationships of Cr2AlB2 are delicately discussed.Meanwhile,as the precursor for fabrication of Cr2AlB2,high purity CrB powders are also prepared by high-temperature reaction of B and Cr elemental powders at 1800℃.CrB grains grow into regular plate-like morphology.Through Rietveld structure refinement,new sets of diffraction data are presented for both CrB and Cr2AlB2 and overlapped peak positions and intensities are revealed which make up for the deficiency of the existing data in ICDD PDF#32-0277(CrB)and ICDD PDF#72-1847(Cr2AlB2).Moreover,since MAB phases are precursors for preparing MBenes,2D-CrBnanosheets are successfully prepared by completely etching out Al atomic layers from Cr2AlB2.2D-CrB crystalizes in CrB structure with two-dimensional lamellar morphology.Simultaneously the formation mechanism of 2D-CrB is vividly depicted.A system of materials preparation from CrB to Cr2AlB2 and then to 2D-CrB is well established.

Validation of different personalized risk models of chemotherapy-induced nausea and vomiting:results of a randomized,double-blind,phase III trial of fosaprepitant for cancer patients treated with high-dose cisplatin

Background:Highly emetogenic chemotherapy induces emesis in cancer patients without prophylaxis.The purpose of this study was to evaluate the efficacy and safety of a fosaprepitant-based triple antiemetic regimen for the prevention of chemotherapy-induced nausea and vomiting(CINV)in patients with solid malignant tumors,determine risk factors and externally validate different personalized risk models for CINV.Methods:This phase III trial was designed to test the non-inferiority of fosaprepitant toward aprepitant in cancer patients who were to receive the first cycle of single-day cisplatin chemotherapy.The primary endpoint was complete response(CR)during the overall phase(OP)with a non-inferiority margin of 10.0%.Logistic regression modelswere used to assess the risk factors ofCRand no nausea.To validate the personalized risk models,the accuracy of the risk scoring systems was determined by measuring the specificity,sensitivity and area under the receiver operating characteristic(ROC)curve(AUC),while the predictive accuracy of the nomogram was measured using concordance index(C-index).Results:A total of 720 patients were randomly assigned.CR during the OP in the fosaprepitant group was not inferior to that in the aprepitant group(78.1%vs.77.7%,P=0.765)with a between-group difference of 0.4%(95%CI,-5.7%to 6.6%).Female sex,higher cisplatin dose(≥70 mg/m2),no history of drinking and larger body surface area(BSA)were significantly associated with nausea.The AUC for the acute and delayed CINV risk indexes was 0.68(95%CI:0.66-0.71)and 0.66(95%CI:0.61-0.70),respectively,and the C-index for nomogram CINV prediction was 0.59(95%CI,0.54-0.64).Using appropriate cutoff points,the three models could stratify patients with high-or low-risk CINV.No nausea and CR rate were significantly higher in the low-risk group than in the high-risk group(P<0.001).Conclusions:Fosaprepitant-based triple prophylaxis demonstrated non-inferior control for preventing CINV in patients treated with cisplatin-base chemotherapy.Female cancer patients without a history of alcohol consumption,with larger BSA and received high-dose cisplatin might be more vulnerable to CINV.Three personalized prediction models were well-validated and could be used to optimize antiemetic therapy for individual patients.

Theoretical prediction on the stability, electronic structure, room and elevated temperature properties of a new MAB phase Mo2AlB2

Mo2AlB2 is a new MAB phase that has been observed in thin foils of Mo Al B during TEM observation and in Na OH etched Mo Al B samples. However, the structural characteristics, chemical bonding and properties of this new compound have not been investigated. In this work, geometry optimized crystal structure of Mo2AlB2 is obtained and its stability, elastic and thermal dynamic properties are investigated. Mo2AlB2 is stable in Al lean conditions, which is consistent with the exiting experimental results. It is also gauged as a damage tolerant or quasi-ductile ceramic based on the low Pugh’s shear to bulk modulus ratio(G/B = 0.544) and positive Cauchy pressure in all three crystallographic directions, which is underpinned by the metallic bonding. Mo2AlB2 also exhibits high stiffness which is attributed to the strong B–B covalent bond chains within its crystal structure. Due to the anisotropic chemical bonding, Mo2AlB2 has anisotropic thermal expansion coefficients αa= 6.19 × 10^–6 K1, αb= 12.13 × 10^-6 K^–1, αc= 6.66 × 10^-6 K^–1,respectively, along a, b and c directions in the temperature range between 300 and 1500 K. The heat capacity from 300 to 1500 K can be described as Cp= 120.32 + 0.01648 T-2.597 × 10^6 T^-2(J·mol^–1·K^–1).The elastic constants decrease almost linearly with temperature. The elastic constants representing the resistance to principle deformation(c11, c22 and c33) decrease in faster rates than those representing shear deformation resistance(c44, c55 and c66). Correspondingly, bulk and Young’s modulus decrease in faster rates than shear modulus. In light of the structure-property relations of Mo2AlB2, it is suggested that future damage tolerant ceramics can be designed by putting stiff covalent bonding units into soft metallic bonding box to obtain both high stiffness and quasi-ductility.