Nucleation of filaments of the TGBA phase in free-standing films

A model of filament nucleation in the twist grain boundary A (TGBA) phase in free-standing smectic films is proposed. It is based on a concept of finite blocks of parallel smectic layers forming a helical structure in the interior of a film. In our model, the blocks resemble twin-like domains in smectic-A liquid crystal. The blocks are mediated to surrounding smectic layers in film either continuously (coherent twin boundary) or discontinuously via dislocation loops wrapping up blocks. Edge components of dislocation loops form incoherent twin boundary. Screw components forming twist grain boundary connect neighbour blocks among themselves. Nucleation of TGBA filament in a film is treated using a simplified model based on isotropic smectic-A elastic theory. Discussion showed that filaments can be nucleated just below the transition temperature from the isotropic to the TGBA phase under slow temperature decrease. The nucleation of dislocation loops is possible due to low compression modulus of material which can be expected just below the transition temperature.     

布洛芬-扑热息痛孪药的合成

以布洛芬（IPF）和扑热息痛（PCM）为原料,无水丙酮和乙酸乙酯为溶剂,二环己基碳二亚胺（DCC）为脱水剂,4-二甲氨基吡啶（DMAP）为催化剂,合成了布洛芬-扑热息痛孪药（PHI）,以重结晶法对目标产物进行纯化,产物结构经IR和1H NMR确定。 探讨了原料比例、脱水剂用量、催化剂用量、反应时间和溶媒用量对目标物产率的影响,并采用正交试验筛选最优合成工艺,最终确定的最优反应条件为:n(PCM)∶n(IPF)=1∶1.5,催化剂的最佳用量为布洛芬质量的10%,反应时间为8 h,溶媒体积为70 mL（V(乙酸乙酯)∶V(丙酮)=1∶1）,在该条件下,目标物PHI的产率为66.53%。     

具有孪晶结构的红细胞状硫化铜的制备及其光芬顿催化性能

采用简单的溶剂热法制备出具有孪晶结构的红细胞状硫化铜材料。研究不同前驱体比例和反应时间对硫化铜产物微观形貌的影响，并对孪晶结构红细胞状硫化铜可能的形成机理进行分析。在可见光照射下孪晶结构红细胞状硫化铜与H₂O₂组成的类芬顿系统表现出优异的降解性能，光照50 min后，亚甲蓝降解率可达95%。对比孪晶结构红细胞状硫化铜与合成的花球状硫化铜的催化性能，结果表明含有孪晶结构的红细胞状硫化铜对亚甲蓝的降解性能更好，说明孪晶的存在有利于加速光生电子-空穴的分离。     

具有孪晶结构的红细胞状硫化铜的制备及其光-芬顿催化性能

采用简单的溶剂热法制备出具有孪晶结构的红细胞状硫化铜材料。研究不同前驱体比例和反应时间对硫化铜产物微观形貌的影响,并对孪晶结构红细胞状硫化铜可能的形成机理进行分析。在可见光照射下孪晶结构红细胞状硫化铜与H₂O₂组成的类芬顿系统表现出优异的降解性能,光照50 min后,亚甲蓝降解率可达95%。对比孪晶结构红细胞状硫化铜与合成的花球状硫化铜的催化性能,结果表明含有孪晶结构的红细胞状硫化铜对亚甲蓝的降解性能更好,说明孪晶的存在有利于加速光生电子-空穴的分离。     

Multiferroic Domain Boundaries as Active Memory Devices: Trajectories Towards Domain Boundary Engineering

Twin boundaries in ferroelastics and curved interfaces between crystalline and amorphous zircon can, in principle, act as multiferroic structural elements and lead the way to the discovery of novel multiferroic devices which are based on structurally heterogeneous materials. While this paradigm has not yet been explored in full, this review shows that physical and chemical properties can vary dramatically inside twin boundaries and interfaces. Properties that have been already been explored include electric dipoles in a non‐polar matrix, the appearance of superconductivity in twin boundaries and the catalytic reaction of hydrous species in interfaces of radiation damaged material. Some of the fundamental physical and chemical properties of twin boundaries and related interfaces are described and possible applications are outlined.     

磁性形状记忆合金Ni50Mn29Ga21Tb1.2室温下的晶体结构研究

采用差热分析和X射线衍射及透射电子显微分析,研究了Ni50Mn29Ga21Tb1.2形状记忆合金的马氏体转变温度、室温下的马氏体的结构及亚结构.结果表明 Ni50Mn29Ga21Tb1.2室温下以体心四方结构的五层马氏体为主,其晶格常数为 a=b=0.60 nm,c=0.5546 nm;在某一微小区域内有体心斜方结构的七层马氏体,其晶格常数为 a=0.616 nm,b=0.581 nm,c=0.553 nm,β=90.8°;Ni50Mn29Ga21Tb1.2室温下的亚结构为孪晶.     

Statistical analysis of S/N-curves by means of a fatigue database for polypropylene

Material databases of plastics are becoming more and more the focus of applied science and commercial use in industry. Material properties of material manufacturers are often provided in publicly accessible material databases, which usually contain processing and mechanical properties under static loadings. Fatigue strength values are usually not accessible. The fatigue data for thermoplastics is of particular interest, as these materials have a particularly high lightweight construction potential and can be processed with a high degree of automation and reproducibility.Individual fatigue strength parameters for a specific material, environmental condition, geometry and loadings have been investigated in numerous publications. However, no work has been found in which fundamental interactions of different materials, environmental conditions, geometries and loadings on the course of the S/N-Curve have been investigated.In this paper, different effect relationships between temperature, filler type and filler content, fiber orientation and load ratio will be presented for the material Polypropylene (PP). A fatigue strength database of 11 different material manufacturers, from 71 different S/N-Curves with 606 tested samples, serves as a basis. The fatigue database enables a digital twin, which is used for the design of structural components to add a third dimension with artificial intelligence, and which is trained by an engineer. From the determined effect relationships, fatigue factors are to be derived and can be used to evaluate the fatigue strength of a component in the design process and to train the digital twin. The fatigue-strength values from the database also allow a statistical consideration of the slope k and the scattering of the S/N-Curve. The different S/N-Curves are transferred into a Haigh diagram, from which the functional course of the mean stress is determined.     

Psuedosymmetry and pseudomerodry or nonmerohedral twinning for the known structure of diaquabis(quinolin‐8‐olato‐κ2N,O)zinc(II)

The structure of the title centrosymmetric compound, [Zn(C₉H₆NO)₂(H₂O)₂], has already been solved three times [Merritt, Cady & Mundy (1954). Acta Cryst. 7 , 473–476; Palenik (1964). Acta Cryst. 17 , 696–700; Chen, Zhang, Shi, Huang, Liang & Zhou (2003). Acta Cryst. E 59 , m814–m815]. The authors of the two most recent papers state that they attained lower R1 values than that obtained in the 1954 paper, but they do not mention that Merritt et al. had derived the structural model from a twinned crystal. Also, from a structural point of view, there are strong indications that the most recent report is in fact the isostructural Cu^II complex already reported by Okabe & Saishu [Acta Cryst. (2001), E 57 , m251–m252] and not the Zn^II complex. The structure of the title compound is reported here based on data obtained from a twinned crystal.     

NONLINEAR OPTICAL PROPERTIES OF MOLECULAR TWINS

Three different series of twin nonlinear optic (NLO) molecules were studied, in which the two NLO chromophores are linked by a central flexible polymethylene spacer. The first series, which had two azobenzene chromophores (Azo-twins), was designed to also exhibit liquid crystallinity. Most of the members of this series exhibited a nematic mesophase. The second series had two 4-nitrophenol units as chromphores (PNP-twins), while the third one was based on 4-alkylsulfonyl-4'-alkoxy azobenzene chromophores (Sulfazo-twins). These twin NLO systems exhibited interesting odd-even oscillations in their second harmonic generation (SHG) efficiencies in the powder form. When the spacer had an odd number of methylene groups, they exhibited significantly higher powder SHG efficiency than their even counterparts, with the even ones most often exhibiting no detectable SH signal. Preliminary single crystal X-ray diffraction studies performed on the PNP-twin series showed that while the even members possess a molecular center of symmetry and pack centro-symmetrically, the odd ones do not, leading to the observed alternation. The orientational-disordering dynamics of two of the twin series – the PNP and the Sulfazo-twin series, doped in a poly(methyl methacrylate) matrix, was also studied by monitoring the SH-signal decay in electric field poled samples. Interestingly, the maximum attainable SH signal, χ⁽²⁾, in the poled samples also showed an odd-even oscillation with the odd ones again exhibiting a higher value of χ⁽²⁾. The temporal stability of the SHG intensity at 70°C, after the removal of the applied corona, was also studied and the relaxation of the chromophores was found to follow a biexponential decay. The slower relaxation component exhibits a spacer length dependence, which suggests the interplay of two factors in governing the temporal stability in such polymer doped twin systems, one is the conformational discomfort experienced by the spacer in adopting a U-shaped geometry, and the other the electrostatic repulsion when two aligned dipoles lie very close to each other.     

Tools to Simulate Distributive Mixing in Twin‐Screw Extruders

The application of the mapping method in finite element modeling is extended to quantitatively compare mixing in different twin‐screw extruder layouts. The mapping method provides volumetric quantities, which are crucial for the analysis and optimization of mixing based on the tracking of particles in the velocity field. A new approach to the mapping method is developed to analyze mixing in complex, dynamic open geometries. Several screw configurations and different types of conveying screws are compared, changing the pitch and gap widths. The volume‐weighted intensity of segregation is used as a mixing measure.

     

钇系涂层超导体金属基带再结晶织构及显微组织

用轧制－再结晶热处理方法制备了强立方织构的纯Ni基带和无磁性Cu-Ni合金基带，为第二代钇钡铜氧高温超导带材提供了较好的基带材料，用三维取向分布函数（ODF）和ψ扫描曲线研究了织构，用金相显微镜研究了截面显微组织。分析表明，Cu0.70Ni0.30合金和纯Ni在再结晶温度为1000℃时，获得最强的立方结构；Cu0.85Ni0.15在900℃时获得最强的立方织构，立方织构强度大小各不相同，3种不同组分金属都获得了均匀的等轴的等轴晶粒组织，其中Cu0.85N0.15的晶粒大于Cu0.70Ni0.30和纯Ni的晶粒，Cu0.85Ni0.15和Cu0.70Ni0.30都出现了退火孪晶。     

Indexing Non-merohedrally Twinned Crystals by Bruker'sAPEX2 and Agilent's CrysAlis~(PRO), an Example of a Crystal Structure That Can Be Refined through Either the PLATONRoute or the ‘HKLF 5' Route,and, Simultaneous Data Collection of Two Crystals in a Tw

The first part of this report describes the data reduction of non-merohedrally twinned crystals measured on Bruker and Agilent area-detector diffractometers. The image frames of methyl-2-aminopyrazine-3-carboxylate were processed with APEX2 to furnish a set of overlapping diffraction indices that were used for solution and refinement. CrysAlisPRO was used for processing the frames of bis(diethyldicarbamato)nickel, which exists in monoclinic and tetragonal polymorphs, and in untwinned and twinned forms. In the second part, the crystal structure of [(3-formyl-4- hydroxyphenyl)methyl]triphenylphosphanium chloride was refined through the ‘HKLF 5'(based on a combined set of diffraction indices) and PLATON(based on one set of diffraction indices) routes to give identical outcomes because the amount of overlap of the twin domains is small. For the third part, in a proof-of-concept investigation, the diffraction pattern of untwinned and twinned 4-{(E)-(4-aminophenyl)diazenyl]phenylamine was recorded simultaneously in one run; the three domains could be indexed and the crystal structure satisfactorily refined. The refinement was identical to those derived from independent measurements; the crystal structure features two independent centrosymmetric molecules, one of which is ordered and the other whole-molecule-disordered. This two-in-one run opens up the possibility that two or more crystals having different atomic compositions can be measured simultaneously if their reciprocal lattices do not overlap significantly.     

Robust liquid crystal droplets

The preparation and properties of cyanobiphenyl liquid crystal droplets encapsulated by the polymerizable lecithin 1,2-bis(10,12-tricosadiynoyl)-sn-glyero-3-phosphocholine (DC_8,9PC) are described. Under a wide variety of preparation conditions the droplets obtain a diameter of approximately 10 mum. These droplets are stable for periods of over one year at room temperature. Furthermore, they are stable upon temperature cycling between the nematic and isotropic phases and between the smectic A to nematic to isotropic phase transitions.     

近红外光谱法最小二乘双胞胎支持向量机的应用研究

依据中药大黄的近红外光谱信息,采用最小二乘双胞胎支持向量机( LSTSVM)算法,通过MATLAB软件编程,建立参数可优化识别模型,实现了对中药大黄的真伪鉴别.将实验材料98个大黄样品随机划分为训练集和测试集,对于训练集60个样品采用留1/5法交叉验证优化模型参数,以所选最优化参数结合训练集样品的近红外光谱建立最优识别模型,对测试集的38个样品的真伪迸行识别,识别率可达97.4％.结果表明,LSTSVM算法是一种有效的识别方法,可依据中药大黄的近红外光谱对其真伪进行快速识别.同时,本研究将大黄样品6次随机划分为训练集和测试集,建模预测平均识别率为93.4％,表明采用LSTSVM算法建立识别模型具有较好的稳健性.     

Synthesis and characterization of liquid–crystalline polyesters with chiral and achiral twin spacers

A series of novel thermotropic main-chain chiral liquid–crystalline random copolyesters consisting of spacers of two different types—chiral and achiral—was synthesized. Polyesters (BmTa) with tartaric acid as the chiral spacer (Ta), aliphatic diols (with ‘m’ = 2–10 methylene groups) as the achiral spacers, and 4,4′-dihydroxy biphenyl (B) as the mesogen were synthesized via condensation polymerization in solution after duly protecting the 2,3-dihydroxy groups of tartaric acid by acetylation. The copolymers were characterized by Fourier transform infrared spectroscopy, ¹H and ¹³C NMR spectra, gel permeation chromatography, and thermogravimetric analysis. Transition temperatures for phase changes recorded by DSC were corroborated with the textures observed by a hot-stage optical polarizing microscope. The wide-angle X-ray diffraction (WAXD) profiles indicated a SmE phase at room temperature. The lower angle region at 2θ = 0.5–2.45 covered by WAXD indicated a layer of thickness of 161 Å, less than the molecular length for B0Ta. The [α_D] values were recorded on a digital polarimeter. The birefringence was lost at higher mesophase temperatures in lower members with m < 5, a behavior found in certain chiral systems, and the higher members with m > 5 showed a lesser number of phase transitions. On cooling, the polyesters produced a texture with the formation of transition bars. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1743–1752, 2001     

Indexing Non-merohedrally Twinned Crystals by Bruker＇sAPEX2 and Agilent＇s CrysAlis~（PRO）, an Example of a Crystal Structure That Can Be Refined through Either the PLATONRoute or the ＇HKLF 5＇ Route,and, Simultaneous Data Collection of Two Crystals in a Two-in-one Run

The first part of this report describes the data reduction of non-merohedrally twinned crystals measured on Bruker and Agilent area-detector diffractometers. The image frames of methyl-2-aminopyrazine-3-carboxylate were processed with APEX2 to furnish a set of overlapping diffraction indices that were used for solution and refinement. CrysAlisPRO was used for processing the frames of bis（diethyldicarbamato）nickel, which exists in monoclinic and tetragonal polymorphs, and in untwinned and twinned forms. In the second part, the crystal structure of [（3-formyl-4- hydroxyphenyl）methyl]triphenylphosphanium chloride was refined through the ‘HKLF 5＇（based on a combined set of diffraction indices） and PLATON（based on one set of diffraction indices） routes to give identical outcomes because the amount of overlap of the twin domains is small. For the third part, in a proof-of-concept investigation, the diffraction pattern of untwinned and twinned 4-{（E）-（4-aminophenyl）diazenyl]phenylamine was recorded simultaneously in one run; the three domains could be indexed and the crystal structure satisfactorily refined. The refinement was identical to those derived from independent measurements; the crystal structure features two independent centrosymmetric molecules, one of which is ordered and the other whole-molecule-disordered. This two-in-one run opens up the possibility that two or more crystals having different atomic compositions can be measured simultaneously if their reciprocal lattices do not overlap significantly.