Thermodynamically stable dispersions induced by depletion interactions

When small particles are added to a colloidal dispersion of large particles, a depletion interaction between large particles occurs because the small ones are depleted from the gaps between the former particles. In the present paper, a cell model is employed to examine the behavior of a dispersion of large particles immersed in an electrolyte solution containing small particles. In this model, each cell consists of one large particle in its center and an associated atmosphere. Double-layer, van der Waals, and depletion interactions, as well as entropic effects, have been taken into account. When the change of the free energy with respect to that of the electrolyte solution is negative (and this happens in most cases), the dispersions of large particles are stable from a thermodynamic point of view. With increasing volume fraction of the small particles, the free energy change becomes more negative. The formation of gels observed experimentally in concentrated emulsions is explained through the formation of a thermodynamically stable dispersion.     

Self-assembly of a novel series of hetero-duplexes driven by donor-acceptor interaction

The self-assembly of a novel series of donor-acceptor interaction-driven artificial hetero-duplexes in organic media has been described. Four linear compounds 1a-1d, bearing two to five electron rich 1,5-dioxynaphthalene units connected by the tetra(ethylene glycol) linker, respectively, have been prepared and used as donors, while eight compounds 2a-2d, 13-16, bearing one to four electron deficient pyromellitic diimide, 1,4,5,8-naphthalene-tetracarboxydiimide, or perylene-3,4,9,10-tetracarboxydiimide units, respectively, have been used as acceptors. The structure of the hetero-duplexes has been characterized by the ¹H NMR, UV-vis spectroscopy and vapor pressure osmometry. It is revealed that the binding stability of the duplexes vary greatly, depending on the length and structure of the monomers and also the solvent, and hetero-duplex 1d·2d displays a maximum association constant of ca. 1.0×10⁴ M⁻¹ in chloroform.     

Self-assembly of a new series of quadruply hydrogen bonded heterotrimers driven by the donor-acceptor interaction

This paper describes the self-assembly of a new series of heterotrimers in chloroform-d by utilizing the cooperative interaction of hydrogen bonding and donor-acceptor interaction. Compounds 1 and 11, in which an 2-ureido-4[1H]-pyrimidinone unit is connected to 34-crown-10 or 36-crown-10, were used as donor monomer, and 2 and 19, in which an 2-ureido-4[1H]-pyrimidinone unit is connected to NDI, were used as acceptor monomer, while linear compound 4, which contains two diamido-1,8-naphthyridines, was used as template. A large tri-p-(t-butyl)phenylmethoxyl group was introduced to 19 in order to compare its assembling behavior with that of 2. Mixing 4 with dimer 1·2 caused 1·2 to fully decompose and to afford 55% of ‘in-in’-oriented heterotrimer 1·4·2. Adding 4 to the solution of 2·11 or 11·19 in chloroform-d also led to full dissociation of the dimers. However, in these systems the ‘in-in’-arranged heterotrimer 2·4·11 or 11·4·19 could be produced exclusively.     

Chemisorption tobacco mosaic virus removal from aqueous solutions and study of virus interaction with active chemisorbent surface by infrared spectroscopy

The interaction of the tobacco mosaic virus with the active surface of an iron-containing adsorbent obtained from lignin by the plasma-catalytic method was studied by IR spectroscopy. The results revealed decomposition of the virus into protein molecules and RNA reacting with the lignin surface via oxygen atoms during the binding of the virus to the sorbent surface. It was assumed that oxygen carboxylate groups interrelate with nanosized iron clusters incorporated into the adsorbent surface structure.     

Rapid determination of methyl salicylate, a plant-signaling compound, in tomato leaves by direct sample introduction and thermal desorption followed by GC-MS

Many plants infested by herbivores or viruses can rapidly produce and accumulate a plant-signaling compound, methyl salicylate (MeSA), in their leaves to activate disease resistance. In the present work, a simple, rapid, and sensitive method was developed for the determination of MeSA in tomato leaves by direct sample introduction and thermal desorption followed by GC-MS. Results show that the proposed method has a low detection limit (0.08 ng mg(-1)) and good precision (RSD = 8.9%). The present method was applied to the investigation of tomato plant defense response to tobacco mosaic virus (TMV) by rapid analysis of volatile compounds in plant leaves. It was found that tomato plants can produce large amounts of MeSA as a defense response to TMV. This indicates that MeSA may be a plant-signaling compound in tomato plant defense response to TMV.     

Investigation of Tomato Plant Defence Response to Tobacco Mosaic Virus by Determination of Methyl Salicylate with SPME-Capillary GC-MS

Headspace SPME was applied to investigation of tomato plant defence response to tobacco mosaic virus (TMV) by determination of compounds emitted from tomato plants at the extraction conditions of 25 °C and 15 min. It was found that TMV-inoculated tomato plant released large amount of methyl salicylate (MeSA) as response to TMV and MeSA concentration changed dramatically with time after inoculation. Gaseous MeSA as a signaling compound could induce in surrounding tomato plants to produce salicylic acid (SA) and synthesize and release MeSA. These results show that MeSA might be an airborne plant-signalling molecule in tomato plant response to TMV. The present method provided low detection limit of 2.0 ng L^–1 and needed little sample preparation time (15 min), so the method makes it easy to find the critical times of tomato plant response to TMV by fast determination of MeSA released from tomato plant.     

FALDI‐based decomposition of an atomic interaction line leads to 3D representation of the multicenter nature of interactions

Atomic interaction lines (AILs) and the QTAIM's molecular graphs provide a predominantly two‐center viewpoint of interatomic interactions. While such a bicentric interpretation is sufficient for most covalent bonds, it fails to adequately describe both formal multicenter bonds as well as many non‐covalent interactions with some multicenter character. We present an extension to our Fragment, Atomic, Localized, Delocalized and Interatomic (FALDI) electron density (ED) decomposition scheme, with which we can measure how any atom‐pair's delocalized density concentrates, depletes or reduces the electron density in the vicinity of a bond critical point. We apply our method on five classical bonds/interactions, ranging from formal either two‐ or three‐center bonds, a non‐covalent interaction (an intramolecular hydrogen bond) to organometallic bonds with partial multicenter character. By use of 3D representation of specific atom‐pairs contributions to the delocalized density we (i) fully recover previous notion of multicenter bonding in diborane and predominant bicentric character of a single covalent C C bond, (ii) reveal a multicenter character of an intramolecular H‐bond and (iii) illustrate, relative to a Schrock carbene, a larger degree of multicenter M C interaction in a Fischer carbene (due to a presence of a heteroatom), whilst revealing the holistic nature of AILs from multicenter ED decomposition. © 2018 Wiley Periodicals, Inc.     

Complexation induced by weak interaction between DNA and PEO-b-P4VP below the CMC of the polymer

The complexation between circular DNA and individual chains of PEO-b-P4VP with a relatively long PEO block and a short P4VP block is highly controllable when the interaction between DNA and the polymer is weak enough. When one circular DNA chain is taken into consideration, and the polymer concentration is far below its critical micelle concentration(CMC), polymer chains are absorbed by DNA chain due to the interaction between the negatively charged DNA chain and the slightly positively charged P4VP block chains. After the adsorption/complexation, the DNA chain is converted into a nanoring(type 1). In the nanoring, the DNA chain is sufficiently wrapped by the polymer and adopts a fully stretched conformation, so that the DNA compact ratio in the nanorings is close to 1. When the polymer concentration is close to but lower than the CMC, the free polymer chains in the solution are adsorbed not only by the DNA chain but also by the polymer chains that have already been adsorbed on the DNA chain. As a result, the circular DNA chain adsorbs more polymer chains, and thus the resultant nanoring(type 2) has a larger width. In the type 2 nanoring, the DNA chain is slightly compressed; the DNA compact ratio is only about 2-3. Therefore, complexation induced by the weak interaction between DNA and PEO-b-P4VP below the CMC can produce narrow-disperse and large nanorings with a perimeter of micrometers, which are difficult to prepare by existing methods.     

The use of chiral interaction reagents in the separation of D(−)-and L(+)-ascorbic acid by ion interaction reversed-phase HPLC

Summary An HPLC reversed-phase ion interaction reagent method is presented, which makes use of chiral compounds as the interaction reagents. By employing the optical isomeric forms of malic, tartaric and mandelic acids as the interaction reagents, a good separation of D(−) and L(+) ascorbic acid has been achieved. The method has also been applied to the identification of vitamin C in some medical formulations. The separation of te enantiomeric forms of DL malic acid has been attempted and a shor discussion is presented about the elution sequence in chromatographic separation of D- and L-enantiomers.     

Synthesis,crystal structure and DNA interaction studies of a 2D cadmium(II) coordination polymer constructed from 2-(2-pyridyl)benzimidazole

A new complex associated with Cd²⁺, [Cd(OH-H₂Bdc)(2-Pbim)]_n (1), (OH-H₂Bdc = 5-hydroxyisophthalic acid, 2-Pbim = 2-(2-pyridyl)benzimidazole), has been synthesised under hydrothermal conditions and characterised by elemental analysis, FT-IR spectroscopy, TG/DTG and fluorescence spectrum. Its in vitro cytotoxicity towards four selected tumour cell lines has been evaluated by an microculture tetrozolium assay, the results suggest that complex 1 displays greater inhibition than the free benzimidazole ligand. On the basis of the combination of absorption titration and fluorescence emission titration, the binding mode of complex 1 to calf thymus DNA has been investigated. Complex 1 can interact with the base pairs of double-helical DNA via the combined mode of intercalation and groove binding with larger binding constants.     

常温常压流光放电合成NH3

在常温常压条件下，应用超强窄脉冲电场在整个反应器内产生的强烈流光主电，将Ｎ２，Ｈ２电离、离解，产生大量的自由原子、离子、自由基等，在定向化学合成反应模型的控制下合成ＮＨ３，其浓度可达３７００ｍｇ／ｍ＾３。     

Quantitation of γ‐aminobutyric acid in equine plasma by hydrophilic interaction liquid chromatography with tandem mass spectrometry

γ‐ Aminobutyric acid is the principal inhibitory neurotransmitter in the central nervous system and regulates the neuronal excitability. There has been anecdotal evidence that γ‐ aminobutyric acid has been used within a few hours prior to competition in equine sports to calm down nervous horses. However, regulating the use of γ‐ aminobutyric acid is challenging because it is an endogenous substance in the horse. γ‐Aminobutyric acid is usually present at low ng/mL levels in equine plasma; therefore, a sensitive method has to be developed to quantify these low background levels. Measuring low concentrations of endogenous γ‐ aminobutyric acid is essential to establish a threshold that can be used to differentiate levels attributable to exogenous administrations of γ‐ aminobutyric acid. A hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method was developed and validated for the quantitation of γ‐ aminobutyric acid in equine plasma. Calibrators were prepared in artificial surrogate matrix consisting of 35 mg/mL equine serum albumin in phosphate buffered saline. Samples were prepared by protein precipitation with acetonitrile. Utilizing this methodology, a total of 403 equine plasma samples collected post‐competition from horses participating in equestrian events in Canada were analyzed.     

3D Reconstruction of Rough Surfaces by SEM Stereo Imaging

 The paper describes the current state of a multidisciplinary research project which aims to apply advanced stereovision methods to the 3D reconstruction of rough surfaces using scanning electron microscopy (SEM) imaging. SEM stereo imaging compares very favourably to atomic force microscopy (AFM) in a medium range corresponding to elevations less than 10 μm and scanned size less than 100 μm. But the interest of the stereoscopic method is that it enables to characterise wider fields with higher elevations.     

Synthesis of 3-Methylbutanal by Strecker Reaction at Unelevated Temperature and in Acidic Systems

It was reported that3-methylbutanal was an important volatile compound in dry-cured ham products1-3.It has been associated with nutty,cheesy and salty notes in Parma ham4and correlated with the aged flavor of hams5.It is also maybe one of the reasons for …     

Synthesis,spectral, crystal structural,antimicrobial, DNA interaction and thermal behavior of some new zinc halide complexes: 3D supramolecular structure of zinc bromide complex

Three new four coordinated zinc(II) complexes have been synthesized and characterized by IR, UV, elemental analysis, ¹H and ¹³C NMR and X-ray single crystal analysis. The elemental analyses of the complexes are in agreement with the general formula of ZnLX₂ wherein L = Schiff base ligand and X = Cl^?, Br^? and I^?. Low molar conductivities in DMF indicated non-electrolyte character of all complexes. Spectroscopic studies well confirmed the coordination via azomethine nitrogens of the ligand to zinc ion. The single crystal X-ray analysis shows that ZnLBr₂ crystallizes in the triclinic crystal system with space group $\mathit{P}\overline{1}$. It contains two crystallographically independent molecules noted as A and B, with both Zn1A and Zn1B being almost in perfect tetrahedral environments (τ₄ = 0.94 for Zn1A and τ₄ = 0.93 for Zn1B). A detailed structural analysis shows that there are three non-classical hydrogen bondings of C–H…Br in the structure. Various C–H…π and C–H…Br interactions play an important role in stabilizing the molecular structure and then give rise to a 3D supramolecular structure of the ZnLBr₂ complex. After characterization, the Schiff base and its complexes were screened in vitro for their antibacterial and antifungal activities by disk diffusion technique. Also the ability of the complexes for DNA cleavage was studied by agarose gel electrophoresis method. Finally, thermal behavior of the complexes has been studied by thermo-gravimetry and then some activation kinetics parameters of decomposition steps were evaluated based on TG/DTG plots.     

Dispersion corrected interaction of polar and nonpolar fluids confined within carbon nanotubes: Density functional theoretical analysis using Grimme's D3 scheme

The structural and flow characteristics of fluids within carbon nanotube (CNT) is dictated by the interaction of fluid molecules within the nanocavity of CNT. Therefore, in the present study, dispersion corrected density functional theory has been used to investigate the structure and interaction of polar and nonpolar molecules within CNT. The present study shows that there is profound effect on the interaction due to dispersion. The interaction energy of the confined water was found to be reduced with increasing distance of the water molecule from the wall of the CNT. The water is preferentially adsorbed over methane due to stronger interaction with CNT over methane. Further, water is preferentially adsorbed over methanol molecule when interaction is calculated without dispersion but after inclusion of dispersion interaction, the calculated results show that the methanol–CNT interaction is stronger than that of water molecule and hence preferentially adsorbed within the CNT as revealed from MD simulation. The present calculation reveals that that the effect of CNT confinement on the IR spectra of the single file water is quite considerable compared to the IR spectra of tetrahedral bulk water cluster. Therefore, the present results might be useful for the separation of polar molecule from nonpolar molecule during fabrication of CNT‐based filter and purification system.     

采用焦分离方法研究共热解时煤与生物质的相互作用及对焦结构和CO2气化反应性的影响

煤与生物质的相互作用已被广泛研究。但是，其相互作用机制通常是基于混合焦样的物理化学结构和反应性而提出。在这项工作中，基于不同形状和粒度将无烟煤与生物质共热解后的混合焦分离，然后通过分析分离后煤焦的结构和反应性来揭示煤与生物质相互作用机制。在热解温度为600和900℃条件下，在固定床反应器中制备了混合有不同比例的秸秆（CS）的无烟煤焦样。采用了电感耦合等离子体发射光谱法（ICP-OES）和X射线衍射（XRD）对煤焦的AAEM浓度和微晶结构进行了检测。利用TGA设备分析了分离后的煤焦与CO₂的气化反应性。结果表明，随着掺混比例从0增加到80%，煤焦中活性K和Mg的浓度逐渐增加，并形成更为无序的碳结构。共热解过程中，更多的AAEM种类被混合物中的煤焦通过挥发分-焦相互作用捕获，而不是随生物质挥发分逸出。同时，热解温度的升高引起了K和Na挥发和失活，也导致石墨化度的降低。而且，CS的添加和更低的热解温度均可提高煤焦的气化反应性。此外，在煤焦的碱性指数AI与反应性指数R_0.5之间建立了较好的线性关系（R²=0.9009），表明在煤与生物质共气化过程中，AAEMs对提高煤焦气化反应活性起主导作用。     

亲水作用加压毛细管电色谱-激光诱导荧光检测法分析痕量核黄素类物质

一种新型的亲水作用毛细管电色谱(HI-CEC)整体柱被应用于加压毛细管电色谱-激光诱导荧光检测(pCEC-LIF)联用法对核黄素类物质的分离分析。采用自组装的pCEC-LIF系统,实现了对痕量核黄素(RF)、黄素单核苷酸(FMN)和黄素腺嘌呤二核苷酸(FAD)的快速分析。在最优的分离检测条件下,3种化合物在8.0 min内完全分离,RF、FMN和FAD的检出限(LOD, S/N=3)分别为5.0×10－11 mol/L、8.0×10－10mol/L和2.5×10－9mol/L,测定线性范围可达3个数量级,精密度良好。方法简便、全分析时间短、灵敏度和选择性高,血清样品分析实验结果良好,可望进一步应用于体液及细胞中核黄素类物质的痕量检测     

Characterization of a 4-miktoarm star copolymer of the (PS-b-PI)3 PS type by temperature gradient interaction chromatography

Temperature gradient interaction chromatography (TGIC) was applied for the separation of a complex miktoarm star copolymer which has one polystyrene (PS) arm and three polystyrene-b-polyisoprene (PS-b-PI) diblock copolymer arms. Such miktoarm star polymers are much more difficult to characterize than branched homopolymers since the byproduct, typically polymers with missing arm(s) or coupled products, have not only different molecular weights but also different compositions. TGIC was able to fully separate the byproducts, and the composition of the molecular species corresponding to the different separated elution peaks was determined by two methods, fractionation/NMR and multiple detection (UV and RI). A reasonable agreement between the results of the two methods was obtained. By using the composition found, the corresponding molecular weights were determined by multi-angle light scattering detection. Based on the composition and the molecular weight we were able to identify the structure of the different molecular species.