The effect of Er doping on the spin reorientation transition in Ho1−xErxAl2

The magnetothermal properties of pseudo binary Ho_1−xEr_xAl₂ alloys have been investigated by heat capacity measurements. Two anomalies are observed in the heat capacity of HoAl₂. A sharp peak at 20 K represents the first order spin reorientation transition, and a second order anomaly occurs in the vicinity of the ferromagnetic transition at 32 K. As Ho is partially replaced by Er in Ho_1−xEr_xAl₂ the sharpness of the first order heat capacity peak diminishes with increasing Er concentration, while the temperature of this transition remains practically unaffected. The second order ferromagnetic transition shifts to higher temperature region with increasing Er concentration. The observed behaviors are explained considering the geometry of 4f charge densities of Ho³⁺ and Er³⁺ and the easy magnetization directions of HoAl₂ and ErAl₂.     

Curvature-coupled hydration of Semicrystalline Polymer Amphiphiles yields flexible Worm Micelles but favors rigid Vesicles: polycaprolactone-based block copolymers

Crystallization processes are in general sensitive to detailed conditions, but our present understanding of underlying mechanisms is insufficient. A crystallizable chain within a diblock copolymer assembly is expected to couple curvature to crystallization and thereby impact rigidity as well as preferred morphology, but the effects on dispersed phases have remained unclear. The hydrophobic polymer polycaprolactone (PCL) is semi-crystalline in bulk (T(m) = 60°C) and is shown here to generate flexible worm micelles or rigid vesicles in water from several dozen polyethyleneoxide-based diblocks (PEO-PCL). Despite the fact that `worms' have a mean curvature between that of vesicles and spherical micelles, `worms' are seen only within a narrow, process-dependent wedge of morphological phase space that is deep within the vesicle phase. Fluorescence imaging shows worms are predominantly in one of two states - either entirely flexible with dynamic thermal undulations or fully rigid; only a few worms appear rigid at room temperature (T < T(m)), indicating suppression of crystallization by both curvature and PCL hydration. Worm rigidification, which depends on molecular weight, is also prevented by copolymerization of caprolactone with just 10% racemic lactide that otherwise has little impact on bulk crystallinity. In contrast to worms, vesicles of PEO-PCL are always rigid and typically leaky. Defects between crystallite domains induce dislocation-roughening with focal leakiness although select PEO-PCL - which classical surfactant arguments would predict make worms - yield vesicles that retain encapsulant and appear smooth, suggesting a gel or glassy state. Hydration in dispersion thus tends to selectively soften high curvature microphases.     

含吖啶基的单环β-内酰胺及噻唑啉酮衍生物的合成及其生物活性

9-吖啶基甲醛芳亚胺席夫碱分别与氯乙酰氯、苄氧乙酰氯在三乙胺作用下产生的烯酮发生[2+2]环加成反应和巯基乙酸的合环反应,合成了9个1-芳基-3-取代-4-(9-吖啶基)-氮杂环丁-2-酮衍生物L1~L6和2-(9-吖啶基)-3-芳基-1,3-噻唑烷-4-酮衍生物T1~T3,对所合成的化合物进行了体外抗癌活性和白细胞共同抗原活性筛选.结构表明,当样品浓度为10μmol/L时,化合物L4对肿瘤细胞HL-60(Leucocythemia人白血病细胞)生长的抑制率为79.4%.当样品浓度为20μg/mL时,化合物L5,L6和T3对细胞分裂周期磷酸酯酶Cdc25B(Cell division cycle 25B phosphatase)的抑制率分别为80.64%,99.75%和99.34%.当样品浓度为20μmol/mL时,化合物L6和T3对CD45(leukocyte common antigen,LCA白细胞共同抗原)蛋白酪氨酸磷酸酶A的抑制率分别为86.12%和91.03%.在此基础上,初步讨论了该类化合物的构效关系.     

NMR-based metabolomics study of the biochemical relationship between sugarcane callus tissues and their respective nutrient culture media

The culture of sugarcane leaf explant onto culture induction medium triggers the stimulation of cell metabolism into both embryogenic and non-embryogenic callus tissues. Previous analyses demonstrated that embryogenic and non-embryogenic callus tissues have distinct metabolic profiles. This study is the follow-up to understand the biochemical relationship between the nutrient media and callus tissues using one-dimensional (1D ¹H) and two-dimensional (2D ¹H–¹³C) NMR spectroscopy followed by principal component analysis (PCA). 1D ¹H spectral comparisons of fresh unspent media (FM), embryogenic callus media (ECM), non-embryogenic callus media (NECM), embryogenic callus (EC), and non-embryogenic callus (NEC), showed different metabolic relationships between callus tissues and media. Based on metabolite fold change analysis, significantly changing sugar compounds such as glucose, fructose, sucrose, and maltose were maintained in large quantities by EC only. Significantly different amino acid compounds such as valine, leucine, alanine, threonine, asparagine, and glutamine and different organic acid derivatives such as lactate, 2-hydroxyisobutyrate, 4-aminobutyrate, malonate, and choline were present in EC, NEC, and NECM, which indicates that EC maintained these nutrients, while NEC either maintained or secreted the metabolites. These media and callus-specific results suggest that EC and NEC utilize and/or secrete media nutrients differently. Fig

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Time and Temperature Dependence of Macro-ion-Macro-ester Equilibrium in the Cationic Polymerization of Tetrahydrofuran by HOSO2F

Reactivity and equilibrium of two active species-tertiary oxonium ion (TOI) and superacid ester (SAE)-in the system of cationic polymerization of tetrahydrofuran (THF) initiated by fluorosulfonic acid (FSO₃H) in dichloromethame has been studied. In the given system, it was found that TOI is mainly responsible for the polymerization at the initial stage; however, the cocentration of TOI decreases rapidly with the progress of polymerization and finally becomes almost untraceable. On the other hand, [SAE] monotonically increases as the polymerization proceeds. The stability of TOI appears less than that of SAE under the given reaction conditions. Results demonstrate that both the progress of polymerization and increase in temperature favor the formation of SAE.     

Plasma activated water: the next generation eco-friendly stimulant for enhancing plant seed germination,vigor and increased enzyme activity,a study on black gram (Vigna mungo L.)

Plasma Chemistry and Plasma Processing - Chemical fertilization in agriculture is threatening to the ecosystem. Therefore, the use of eco-friendly stimulant for crop revolution is highly desirable....     

Effects of Snap-Off in Imbibition in Porous Media with Different Spatial Correlations

Quasi-static imbibition was simulated using random and correlated stochastic network models. Using the snap-off pore-scale displacement observed by Lernormand et al. (1983) the effects of many parameters on relative permeabilities and residual saturation reported in the literature were reproduced and explained. Increased relative permeabilities and decreased residual non-wetting phase saturation were the results of an increased contact angle (Li and Wardlaw, 1986b; Gauglitz and Radke, 1990; Blunt et al., 1992; Mogensen and Stenby, 1998) a decreased pore–throat aspect ratio, the presence of long-range pore-pore size correlations (Iaonnidis and Chatzis, 1993; Blunt, 1997a), or local pore–throat correlations (Jerauld and Salter, 1990; Iaonnidis and Chatzis, 1993). By modifying the level of snap-off, or its spatial distribution, these parameters varied the efficiency of the displacement patterns and ultimately affect relative permeabilities and residual saturations. Mani and Mohanty (1999) performed simulations on networks with infinite-ranged fractional Brownian motion (fBm) correlations and reported trends of relative permeabilities and residual saturations that were opposite to others’ results (Ioannidis and Chatzis, 1993; Blunt, 1997a). Applying a cut-off length to the fBm correlations reversed Mani and Mohanty’s trends to conform with the common observations.     

Diastereoselective aziridination of 2-B(pin)-substituted allylic alcohols: an efficient approach to novel organoboron compounds

We report that 2-B(pin)-substituted allylic alcohols are good substrates for diastereoselective aziridinations in the presence of PhI(OAc)(2) and N-aminophthalimide. Under the aziridination conditions, the valuable B-C bond remains intact, affording a variety of novel boron-substituted aziridines in good yields and excellent diastereoselectivities. Oxidation of the aziridine B-C bond enables generation of syn-1,3-aminohydroxy-2-ketones with high diastereoselectivity.     

Specific interactions and binding free energies between thermolysin and dipeptides: molecular simulations combined with ab initio molecular orbital and classical vibrational analysis

Thermolysin (TLN) is a metalloprotease widely used as a nonspecific protease for sequencing peptide and synthesizing many useful chemical compounds by the chemical industry. It was experimentally shown that the activity and functions of TLN are inhibited by the binding of many types of amino acid dipeptides. However, the binding mechanisms between TLN and dipeptides have not been clarified at the atomic and electronic levels. In this study, we investigated the binding mechanisms between TLN and four dipeptides. Specific interactions and binding free energies (BFEs) between TLN and the dipeptides were calculated using molecular simulations based on classical molecular dynamics and ab initio fragment molecular orbital (FMO) methods. The molecular systems were embedded in solvating water molecules during calculations. The calculated BFEs were qualitatively consistent with the trend of the experimentally observed inhibition of TLN activity by binding of the dipeptides. In addition, the specific interactions between the dipeptides and each amino acid residue of TLN or solvating water molecules were elucidated by the FMO calculations.