Strong Pauli paramagnetic effect in the upper critical field of KCa2Fe4As4F2

Recently, 12442 system of Fe-based superconductors has attracted considerable attention owing to its unique double-Fe As-layer structure. A steep increase in the in-plane upper critical field with cooling has been observed near the superconducting transition temperature, Tc, in KCa2Fe4As4F2 single crystals. Herein, we report a high-field investigation on upper critical field of this material over a wide temperature range, and both out-of-plane(H∥c, Hc2c) and in-plane(H∥ab, Hc2ab ) directions have been measured.A sublinear temperature-dependent behavior is observed for the out-of-plane Hc2c , whereas strong convex curvature with cooling is observed for the in-plane Hc2ab . Such behaviors could not be described by the conventional Werthamer-Helfand-Hohenberg(WHH) model. The data analysis based on the WHH model by considering the spin aspects reveals a large Maki parameter α=9,indicating that the in-plane upper critical field is affected by a very strong Pauli paramagnetic effect.     

Electroluminescence efficiency in bilayer organic light-emitting devices with LiF/Al cathode

An analytical model to calculate electroluminescence (EL) efficiency of bilayer organic light-emitting devices, considering the influence of introducing LiF insulating buffer layer at metal/organic interface on the barrier height for electron injection, was presented. The relations of EL efficiency versus the applied voltage and injection barrier or internal interfacial barrier or the thickness of organic layer were discussed. The results indicate that: (1) when δ e/δ h < 2, metal/organic (M/O) interface is ohmic contact; when δ e/δ h > 2, M/O becomes contact limited; and when δ e/δ h = 2 (Φ h ～ 0.2 eV, Φ e ～ 0.3 eV), there is a transition from ohmic contact to contact limited; (2) η EL decreases with the increase of δ′e / δ′h; however, when δ′e / δ′h > 2.5 (H ′h～ 0.2 eV, H ′e～ 0.4 eV), the changes of η EL are very small, which shows that η EL is dominated by the carrier’s injection; (3) when increasing Lh/L, η R has a descending trend at low voltage and a rising one at higher voltage. For a given Lh/L, η EL first increases and then decreases with the increasing applied voltage, and as Lh/L further increases, the variation tendency of η EL is more obvious. These conclusions are in agreement with the reported theoretic and experimental results.     

Occurrence of Phthalate Esters in Peri-urban Surface/Deep Soils from Metropolitan City-Beijing

Peri-urban environmental issues are worldwide regarded.The traditional outskirts of Beijing,out of the 4~(th) Ring Road,are undergoing great changes and have been going to be the 'urban area' with the 'circle-spread feature' of city expanding.For the valid use of land and the safety of public health,the assessing of peri-urban soil sanitation appeared to be so essential.     

激发态1，2-二硫环丁烯去活性和异构化机理的理论研究

运用完全活性空间多组态CASSCF方法研究了激发态1,2-二硫环丁烯（1,2-Dithiete）势能面交叉机理．自旋．轨道耦合（SOC）常数采用完全Pauli-Breit旋轨耦合算符（包括单电子和双电子项）进行计算,其强度为198．37或211．35cm^-1,对不同自旋态跃迂起着重要作用．研究结果表明：光激发1,3-dithiol-2-one导致形成主要产物trans—dithioglyoxal（Trans-MinS0）和次级产物thiolthioketene．计算与实验观察结果一致．     

联二烯丁基硫醚衍生物合成呋喃的反应

本文报道以联二烯丁基硫醚为起始物的呋喃衍生物的合成方法.实验结果表明,β-联二烯丁基硫醚醇在氢化钠的作用下以很高的收率环化生成一个苯硫基离去的呋喃产物,β-联二烯丁基硫醚醛与外加亲核试剂作用后能得到多一个取代的类似呋喃产物,而β-联二烯丁基硫醚酮在P2O5的促进下也能环化生成呋喃衍生物.     

The separation single-wall carbon nanotubes on length by sepharose gel

The separations of single-wall carbon nanotubes on length by sepharose gel were investigated in this work. The solutions of sodium dodecyl sulfate and sodium deoxycholate were applied as the eluent in sequence. SEM and Raman were used to characterize the length of nanotube bundles. The results show that the longer nanotubes were eluted out first, and then the shorter tubes were followed by the sodium dodecyl sulfate. However, the separated order was totally reversed by the sodium deoxycholate. By this method, the process generated nanotube fractions not only were narrower in length distributions, but also could control the separation orders by changing the eluents. Moreover, the separation principle was also discussed.     

三电极气体开关自陡化技术及应用

根据Trigatron的触发要求设计了脉冲变压器型驱动源、三电极气体开关。在多种驱动模式下对三电极开关的自陡化参数进行统计分析,选择最优的自陡化工作模式。通过研究自陡化工作模式,优化了三电极开关工作极性、工作电场、紫外辐照强度和辐照时间。试验结果表明：增加陡化环节后,Trigatron的击穿概率有了明显提高,击穿时刻延迟和抖动明显降低,扩大了Trigatron稳定工作的欠压比范围。     

气相中Cu+和Zn+与CS2反应的计算研究

以Cu⁺和Zn⁺与CS₂反应作为第一过渡金属离子与CS₂反应的范例体系. 采用密度泛函UB3LYP/6-311+G^*方法计算研究了第一过渡金属离子在基态和激发态与CS₂反应的反应机理. 全参数优化了反应势能面上各驻点的几何构型, 用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证. 并用UCCSD(T)/6-311G^*方法对各驻点作了单点能量校正. 在Cu⁺与CS₂反应中, 计算了单重态初始中间体¹IM1到三重态插入型中间体³IM2的反应交叉势能面. 确定了第一过渡金属离子与CS₂的反应为插入-消去反应, 找到了基态和激发态金属离子与CS₂反应的主要通道.     

In situ annealing effects on magnetic properties and variable-range hopping of iron-based ladder material BaFe2S3

正All iron-based superconductors,regardless of their detailed crystal structure,share the same conductive Fe_2X_2(X=As,P,Se,and S)layers as the crucial structural unit[1-8].In the Fe_2X_2 layers,edge-shared FeX_4 tetrahedra form a square lattice in quasi-two-dimensional(quasi-2D)planes.One may wonder what kind of properties will be manifested in the quasi-one-dimensional(quasi-1D)counterparts exhibiting an identical coordination as the above-mentioned quasi-2D     

Low temperature specific heat of 12442-type KCa2Fe4As4F2 single crystals

The Hubble constant H_0 represents the expansion rate of the Universe at present and is closely related to the age of the Universe.The accurate measurement of Hubble constant is crucial for modern cosmology.However,different cosmological observations give diverse values of Hubble constant in literature.Up to now,there are two methods to measure the Hubble constant.One is to directly measure the Hubble constant based on distance ladder estimates of Cepheids and so on.The other is to globally fit the Hubble constant under the assumption of a cosmological model,for example the "standard" ACDM model.Adopting the low-redshift observational datasets,including the Pantheon sample of Type Ⅰa supernovae,baryon acoustic oscillation measurements,and the tomographic Alcock-Paczynski method,we determine the Hubble constant to be 67.95_(-1.03)~(+0.78),69.81_(-2.70)~(+2.22) and66.75_(-4.23)~(+3.42) km s~(-1) Mpc~(-1) at 68% confidence level in the △CDM,wCDM and W_0W_a CDM models,respectively.Compared to the Hubble constant given by Riess et al.in 2019,we conclude that the new physics beyond the standard △CDM model is needed if all of these datasets are reliable.