The structure and symmetry of crystalline solid solutions: a general revision

Mixed single crystals composed of host and guest organic molecules of similar structures and shapes are shown to comprise sectors with different host-guest distributions and to have symmetries lower than that of the host crystal. These properties are determined by the structure of the guest and the surface structures of the crystal faces through which the guest molecules are occluded. This general concept is illustrated by studies of three mixed crystal systems,(E)-cinnamamide-(E)-2-thienylacrylamide, (E)-cinnamamide-(E)-3-thienylacrylamide, and(S)-asparagine-(S)-aspartic acid, with x-ray and neutron diffraction and solid-state photochemistry.     

Guest-dependent spin crossover in a nanoporous molecular framework material

The nanoporous metal-organic framework Fe2(azpy)4(NCS)4.(guest) (azpy is trans-4,4'-azopyridine) displays reversible uptake and release of guest molecules and contains electronic switching centers that are sensitive to the nature of the sorbed guests. The switching of this material arises from the presence of iron(II) spin crossover centers within the framework lattice, the sorbed phases undergoing "half-spin" crossovers, and the desorbed phase showing no switching property. The interpenetrated framework structure displays a considerable flexibility with guest uptake and release, causing substantial changes in the local geometry of the iron(II) centers. The generation of a host lattice that interacts with exchangeable guest species in a switchable fashion has implications for the generation of previously undeveloped advanced materials with applications in areas such as molecular sensing.     

Dynamics of water molecules in aqueous solvation shells

We report on the direct measurement of the dynamics of water molecules in the solvation shell of an ion in aqueous solution. The hydrogen-bond dynamics of water molecules solvating a Cl-, Br-, or I- anion is slow compared with neat liquid water, indicating that the aqueous solvation shells of these ions are rigid. This rigidity can play an important role in the overall dynamics of chemical reactions in aqueous solution. The experiments were performed with femtosecond midinfrared nonlinear spectroscopy, because this technique allows the spectral response of the water molecules in the solvation shell to be distinguished clearly from that of the other water molecules in the solution.     

Direct observation and quantification of CO₂ binding within an amine-functionalized nanoporous solid

Understanding the molecular details of CO(2)-sorbent interactions is critical for the design of better carbon-capture systems. Here we report crystallographic resolution of CO(2) molecules and their binding domains in a metal-organic framework functionalized with amine groups. Accompanying computational studies that modeled the gas sorption isotherms, high heat of adsorption, and CO(2) lattice positions showed high agreement on all three fronts. The modeling apportioned specific binding interactions for each CO(2) molecule, including substantial cooperative binding effects among the guest molecules. The validation of the capacity of such simulations to accurately model molecular-scale binding bodes well for the theory-aided development of amine-based CO(2) sorbents. The analysis shows that the combination of appropriate pore size, strongly interacting amine functional groups, and the cooperative binding of CO(2) guest molecules is responsible for the low-pressure binding and large uptake of CO(2) in this sorbent material.     

Guest transport in a nonporous organic solid via dynamic van der Waals cooperativity

A well-known organic host compound undergoes single-crystal-to-single-crystal phase transitions upon guest uptake and release. Despite a lack of porosity of the material, guest transport through the solid occurs readily until a thermodynamically stable structure is achieved. In order to actively facilitate this dynamic process, the host molecules undergo significant positional and/or orientational rearrangement. This transformation of the host lattice is triggered by weak van der Waals interactions between the molecular components. In order for the material to maintain its macroscopic integrity, extensive cooperativity must exist between the molecules throughout the crystal, such that rearrangement can occur in a well-orchestrated fashion. We demonstrate here that even weak dispersive forces can exert a profound influence over solid-state dynamics.     

羟丙基-β-环糊精包埋性能研究

以复合物稳定常数为指标对羟丙基-β-环糊精（HPCD）与不同客体形成复合物的性能进行了研究。HPCD的取代度和取代基分布由甲基化分析测定。选取苯甲酸乙酯、甲基红和酚酞分别作为大小和构型不同的客体模型与HPCD作用,结合HPCD的结构特性,总结出了HPCD对不同客体的包埋规律。对于“较小”分子,HPCD的包埋能力远高于母体β-环糊精,羟丙基的“增溶”效应特别明显;对于“中等”分子,HPCD的包埋能力高于母体β-环糊精,低取代度时,羟丙基以“增溶”效应为主;对于“较大”分子,空间位阻是主导效应,HPED包埋能力低于β-环糊精。     

花生壳生物炭用量对猪粪堆肥温室气体和NH3排放的影响

为研究不同花生壳生物炭添加比例对猪粪堆肥过程中温室气体和NH3排放的影响。利用强制通风静态堆肥技术,研究0(对照)、3%、6%和9%花生壳生物炭添加比例(质量比)对猪粪堆肥过程CO_2、CH_4、N_2O和NH_3排放和堆肥性质的影响。结果表明:添加生物炭能够延长堆肥高温期持续天数,使pH提高0.09～0.13个单位,EC提高11.7%～50.6%;各堆肥处理CO_2、CH_4和N_2O排放速率均随发酵时间的延长呈先升高后降低的趋势,且CO_2、CH_4和N_2O排放速率均与pH具有显著的相关性;随生物炭用量的增加,猪粪堆肥过程中CO_2排放速率表现为先升高后降低的变化趋势,其中以3%生物炭添加比例处理最高,其平均CO_2排放速率比对照增加12.9%;N_2O排放和NH_3挥发均以9%生物炭添加比例处理最低,分别比对照降低12.5%和29.9%。综上,在整个堆肥过程中,花生壳生物炭的添加降低了N_2O和CH_4的累积排放量,且随花生壳生物炭添加比例的增加,温室气体减排效应增大。     

Isolating the spectroscopic signature of a hydration shell with the use of clusters: superoxide tetrahydrate

Cluster spectroscopy, aided by ab initio theory, was used to determine the detailed structure of a complete hydration shell around an anion. Infrared spectra of size-selected O(2)-. (H(2)O)(n) (n = 1 to 4) cluster ions were obtained by photoevaporation of an argon nanomatrix. Four water molecules are required to complete the coordination shell. The simple spectrum of the tetrahydrate reveals a structure in which each water molecule is engaged in a single hydrogen bond to one of the four lobes of the pi* orbital of the superoxide, whereas the water molecules bind together in pairs. This illustrates how water networks deform upon accommodating a solute ion to create a distinct supramolecular species.     

Free Radicals and Reactive Molecules in Clathrate Cavities

Reactive molecules and free radicals, when located in the cavities of the water clathrate lattice, can be prevented from recombining at temperatures almost up to the decomposition point of the lattice. The active species are produced by selective photochemical dissociation of the guest molecules in the clathrate compounds. Data taken from water clathrates of H(2)S, CH(3)SH, and C(2)H(5)SH suggest that S(2), CH(3)S and C(2)H(5)S can be preserved in this way.     

Stable low-pressure hydrogen clusters stored in a binary clathrate hydrate

Thermodynamic, x-ray diffraction, and Raman and nuclear magnetic resonance spectroscopy measurements show that clusters of H2 can be stabilized and stored at low pressures in a sII binary clathrate hydrate. Clusters of H2 molecules occupy small water cages, whereas large water cages are singly occupied by tetrahydrofuran. The presence of this second guest component stabilizes the clathrate at pressures of 5 megapascals at 279.6 kelvin, versus 300 megapascals at 280 kelvin for pure H2 hydrate.     

仿生产仔箱对家兔繁殖性能及母性行为的影响

为了满足福利养兔和严寒地区家兔繁殖生产的需求,对根据家兔生物学特性研制出的仿生产仔箱进行使用效果研究。结果表明,仿生产仔箱有提高巢箱温度的作用,每日早、中、晚分别较外挂式产仔箱提高1.85,2.04,2.57℃(P0.01);部分繁殖性状指标提高。使用仿生产仔箱的母兔泌乳力、断奶数及成活率均较高,母兔拉毛时间提前,拉毛数量有增加的趋势;哺乳期间母兔护仔能力也增强,母兔、仔兔均可得到较好的休息。仿生产仔箱能满足寒冷地区兔群繁殖的需要,符合福利养兔对产仔窝的要求。     

Molecular recognition at crystal interfaces

Nucleation, growth, and dissolution of crystals have been studied by stereochemical approach involving molecular recognition at interfaces. A methodology is described for using ;;tailor-made' additives designed to interact stereospecifically with crystal surfaces during growth and dissolution. This procedure was instrumental in controlling crystal morphology and in revising the concept of the structure and symmetry of solid solutions. Consequently, it was applied to the transformation of centrosymmetric single crystals into solid solutions with polar arrangement displaying second-harmonic generation and to the performance of asymmetric synthesis of guest molecules inside centrosymmetric host crystals. The method has led to a discovery of a new ;;relay' mechanism explaining the effect of solvent on crystal growth. Finally, it allowed for the design of auxiliary molecules that act as promoters or inhibitors of crystal nucleation that can be used to resolve enantiomers and crystallize desired polymorphs.     

Fluorous nanodroplets structurally confined in an organopalladium sphere

The distinct properties of fluorous phases are practically useful for separation, purification, and reaction control in organic synthesis. Here, we report the formation of a liquid-like fluorous droplet, composed of 24 perfluoroalkyl chains confined in the interior of a 5-nanometer-sized, roughly spherical shell that spontaneously assembled in solution from 12 palladium ions and 24 bridging ligands. Crystallographic analysis confirmed the rigid shell framework and amorphous interior. Perfluoroalkanes can dissolve in this well-defined fluorous phase, whereas they can hardly dissolve in a surrounding polar organic solution, and their solubility (up to approximately eight perfluoroalkane molecules per spherical complex) can be finely controlled by tuning the length of perfluoroalkyl chains tethered to the shell.     

The structure of the first coordination shell in liquid water

X-ray absorption spectroscopy and x-ray Raman scattering were used to probe the molecular arrangement in the first coordination shell of liquid water. The local structure is characterized by comparison with bulk and surface of ordinary hexagonal ice Ih and with calculated spectra. Most molecules in liquid water are in two hydrogen-bonded configurations with one strong donor and one strong acceptor hydrogen bond in contrast to the four hydrogen-bonded tetrahedral structure in ice. Upon heating from 25 degrees C to 90 degrees C, 5 to 10% of the molecules change from tetrahedral environments to two hydrogen-bonded configurations. Our findings are consistent with neutron and x-ray diffraction data, and combining the results sets a strong limit for possible local structure distributions in liquid water. Serious discrepancies with structures based on current molecular dynamics simulations are observed.     

云南紫溪山人工巢箱招引鸟类研究初报

为了解紫溪山省级自然保护区次级洞巢鸟类在繁殖期对人工巢箱的利用情况,于2019年,在云南紫溪山安放了42个人工巢箱。通过调查人工巢箱的利用情况,发现42个巢箱共有16个巢箱分别被栗臀?(Sitta nagaensis)、大山雀(Parus cinereus)、绿背山雀(Parus monticolus)利用,其中栗臀?利用4个,大山雀利用4个,绿背山雀利用8个。大山雀和绿背山雀以B号巢箱和C号巢箱为选择对象,而栗臀?以A号巢箱和B号巢箱为选择对象。 同时,绿背山雀利用的两个巢箱出现了二次利用现象。本研究对扩大紫溪山次级洞巢类益鸟种群有一定的指导意义。     

葡萄酒灌装线自动码垛机的技术改造

介绍了自动码垛机的概念、分类,重点阐述了葡萄酒灌装线码垛机的结构、工作过程及原理,分析了葡萄酒灌装过程中自动码垛机在对小箱(1×6瓶)进行码垛后出现的掉箱现象的原因,并进行了技术改造。改造后在不增加托盘尺寸的条件下,每垛箱子数量由120箱增加到145箱,提高了箱垛的稳定性,大大降低了掉箱的概率,同时减少了仓库存储的占地面积。     

高原蚕区家蚕茧层率遗传分析

旨在验证并丰富家蚕茧层率性状的遗传规律,为培育高茧层率的家蚕纯种提供理论依据。以高丝量品种‘菁松’、‘皓月’和中丝量品种‘芙蓉’、‘湘晖’为亲本,构建5世代遗传群体,运用多世代联合分析方法分析茧层率的遗传规律。结果表明：家蚕茧质性状具有明显的性别效应,雄性茧层率大于雌性;亲本的茧层率性状与茧层量呈显著正相关;F₁代的茧层率介于两亲本之间,反交组合茧层率高于正交组合;回交群体的频数呈双峰或偏态的单峰分布;茧层率的杂种优势率在-3.82%~5.63%之间,几乎没有杂种优势。研究得出结论为茧层率高值对低值为显性,呈偏母本遗传,遗传体系中存在主基因,可能存在于性染色体上。     

Probing the solvent-assisted nucleation pathway in chemical self-assembly

Hierarchical self-assembly offers a powerful strategy for producing molecular nanostructures. Although widely used, the mechanistic details of self-assembly processes are poorly understood. We spectroscopically monitored a nucleation process in the self-assembly of p-conjugated molecules into helical supramolecular fibrillar structures. The data support a nucleation-growth pathway that gives rise to a remarkably high degree of cooperativity. Furthermore, we characterize a helical transition in the nucleating species before growth. The self-assembly process depends strongly on solvent structure, suggesting that an organized shell of solvent molecules plays an explicit role in rigidifying the aggregates and guiding them toward further assembly into bundles and/or gels.     

Toll-like receptor 4-dependent activation of dendritic cells by beta-defensin 2

beta-Defensins are small antimicrobial peptides of the innate immune system produced in response to microbial infection of mucosal tissue and skin. We demonstrate that murine beta-defensin 2 (mDF2beta) acts directly on immature dendritic cells as an endogenous ligand for Toll-like receptor 4 (TLR-4), inducing up-regulation of costimulatory molecules and dendritic cell maturation. These events, in turn, trigger robust, type 1 polarized adaptive immune responses in vivo, suggesting that mDF2beta may play an important role in immunosurveillance against pathogens and, possibly, self antigens or tumor antigens.     

Scandium clusters in fullerene cages

The production and spectroscopic characterization of fullerene-encapsulated metal-atom clusters is reported. In particular, both solution and solid-state electron paramagnetic resonance (EPR) spectra of Sc(3)C(82) have been obtained. ScC(82) also gives an EPR spectrum, but Sc2Cn species-the most abundant metallofullerenes in the mass spectrum-are EPR-silent even though Sc(2) is EPR-active in a rare-gas matrix at 4.2 K. The results suggest that the three scandium atoms in Sc(3)C(82) form an equilateral triangle-as was previously suggested for Sc(3) molecules isolated in a cryogenic rare-gas matrix. The spectrum of ScC(82) has features similar to those found earlier for LaC(82) and YC(82), suggesting that it can also be described as a +3 metal cation within a -3 fullerene radical anion. An implication of this work is that production of macroscopic quantities of clustercontaining fullerenes may make possible the fabrication of exotic new structures with regular arrays of metal-atom clusters isolated in fullerene molecules, resulting in a new type of host/guest nanostructured material.