Densely Packed Hydrophobic Clustering: Encapsulated Valerates Form a High‐Temperature‐Stable {Mo132} Capsule System

Porous molecular nanocontainers of {Mo₁₃₂}‐type Keplerates offer unique opportunities to study a wide variety of relevant phenomena. An impressive example is provided by the highly reactive {Mo₁₃₂‐CO₃} capsule, the reaction of which with valeric acid results in the very easy release of carbon dioxide and the uptake of 24 valerate ions/ligands that are integrated as a densely packed aggregate, thus indicating the unique possibility of hydrophobic clustering inside the cavity. Two‐dimensional NMR techniques were used to demonstrate the presence of the 24 valerates and the stability of the capsule up to ca. 100 °C. Increasing the number of hydrophobic parts enhances the stability of the whole system. This situation also occurs in biological systems, such as globular proteins or protein pockets.     

基于Lasso-Lars的密井网水驱注水量影响因素分析

目前大部分油藏工程都需要合理的注水量调整方案,为了准确预测注水量则需要分析注水量的影响因素及其之间的关系。通过lasso方法可将模型的系数进行压缩使之变小趋于0,利用lars算法可有效解决lasso的求解问题并记录正则化参数λ所有可能取值下对应的lasso优化问题的解,求得lasso正则化路径.应用lasso-lars正则化路径,得到每一个注水井注水量影响因素对应的回归系数及回归系数变化走势图,确定不同影响因素对注水井注水量的敏感程度.同时证明该方法相对于其他方法的有效性及优越性,对注水量预测模型的建立具有重要意义.     

Directed Self‐Assembly Pathways of Active Colloidal Clusters

Despite the mounting interest in synthetic active particles, too little is known about their assembly into higher‐order clusters. Here, mixing bare silica particles with Janus particles that are self‐propelled in electric fields, we assemble rotating chiral clusters of various sorts, their structures consisting of active particles wrapped around central “hub” particles. These clusters self‐assemble from the competition between standard energetic interactions and the need to be stable as the clusters rotate when the energy source is turned on, and fall apart when the energy input is off. This allows one to guide the formation of intended clusters, as the final structure depends notably on the sequence of steps in which the clusters form.     

Linear extensions of orderings

A construction is given which makes it possible to find all linear extensions of a given ordered set and, conversely, to find all orderings on a given set with a prescribed linear extension. Further, dense subsets of ordered sets are studied and a procedure is presented which extends a linear extension constructed on a dense subset to the whole set.     

Probing Single Nanometer-scale Particles with Scanning Tunneling Microscopy and Spectroscopies

Scanning tunneling microscopy can be used to isolate single particles on surfaces for further study. Local optical and electronic properties coupled with topographic information collected by the scanning tunneling microscope (STM) give insight into the intrinsic properties of the species under study. Since each spectroscopic measurement is done on a single particle, each sample is monodisperse, regardless of the degree of heterogeneity of the original preparation. We illustrate this with three example systems – a metal cluster of known atomic structure, metal nanoparticles dispersed from colloid suspensions, and metallocarbohedrenes (Met-Cars) deposited with other reaction products. Au and Ag nanoparticles were imaged using a photon emission STM. The threshold voltage, the lowest bias voltage at which photons are produced, was determined for Au nanoparticles. Electronic spectra of small clusters of Ni atoms on MoS₂ were recorded. Preliminary images of Zr-based Met-Car-containing soot were obtained on Au and MoS₂ substrates and partial electronic spectra were recorded of these possible Met-Car particles.     

Experiments with active and driven synthetic colloids in complex fluids

In this review, we focus on recent experimental research involving active colloidal particles of non-biological origin evolving in non-Newtonian fluids. This includes self-propelling active particles and particles driven by external fields. We present different propulsion strategies that are either enabled, or strongly modified, by the presence of a complex medium. This paves the way for novel mechanisms of active transport in biofluids or in other non-Newnotian fluids. When considering the medium, we differentiate between disordered complex fluids, such as diluted polymer solutions, and liquid crystals. While the latter are also viscoelastic fluids, the ability to control their molecular orientation results in distinct colloidal driving and steering mechanisms, and enables new types of active soft matter in the form of active quasi-particles.     

A guide to design the trajectory of active particles: From fundamentals to applications

Active particles convert external energy into motility, displaying a variety of dynamical features. Recent progress in the field has marked a shift in focus from understanding the origin and sources of active motion to controlling the dynamics and trajectory of individual microswimmers. This review explores the advancements made in a two-fold perspective—the role of particle design and that of external factors. Our main goal is to highlight the guiding principles, which determine active particle trajectory. These include, on the one hand, the role of the morphology of active particles and their assemblies in driving translation, rotation, and corresponding coupling between the two. On the other hand, the effect of environmental parameters such as the presence of physicochemical heterogeneities including interfaces, suspended obstacles, and boundaries on the modality and trajectory of active colloids. We discuss the potential of using active particles in biomedical and environmental applications through recent examples.