Controlling the gelation temperature of biomimetic polyisocyanides

The gelation temperature and mechanical properties of aqueous ethylene glycol-decorated polyisocyanide solutions strongly depends on the length of the glycol tail. Copolymerisation of monomers with different tail lengths allows for precise engineering of the gel properties.     

Ice Melting to Release Reactants in Solution Syntheses

Aqueous solution syntheses are mostly based on mixing two solutions with different reactants. It is shown that freezing one solution and melting it in another solution provides a new interesting strategy to mix chemicals and to significantly change the reaction kinetics and thermodynamics. For example, a precursor solution containing a certain concentration of AgNO₃ was frozen and dropped into a reductive NaBH₄ solution at about 0 °C. The ultra‐slow release of reactants was successfully achieved. An ice‐melting process can be used to synthesize atomically dispersed metals, including cobalt, nickel, copper, rhodium, ruthenium, palladium, silver, osmium, iridium, platinum, and gold, which can be easily extended to other solution syntheses (such as precipitation, hydrolysis, and displacement reactions) and provide a generalized method to redesign the interphase reaction kinetics and ion diffusion in wet chemistry.     

Dynamic analysis of a rigid-flexible inflatable space structure coupled with control moment gyroscopes

The vibration generated by the inflatable structure after deployment has a great impact on the performance of the payloads. In this paper, the influence of the control moment gyroscopes (CMGs) on the dynamic responses and characteristics of an inflatable space structure is studied, based on the flexible multibody dynamics in a combination of the absolute nodal coordinate formulation (ANCF) and the natural coordinate formulation (NCF). Firstly, the ANCF and NCF are used to accurately describe the large deformations and large overall motions of flexible inflatable tubes and rigid satellites, respectively. Then, instead of modeling gyroscopic flexible bodies, this paper pioneers a rigid body dynamic model of the CMG in detail by using the NCF modeling scheme, which can be attached to and coupled with any flexible bodies without any assumptions. Then, the orbital dynamic equations of the inflatable space structure coupled with distributed CMGs are obtained by considering the effects of Coriolis force, centrifugal force, and gravity gradient through coordinate transformation. The dynamic characteristics of the inflatable space structure are also analyzed by deriving the eigenvalue problem of a flexible multibody system. Finally, the accuracy of the CMG dynamic model is verified via a classic heavy top example. Several numerical examples are presented to study the influence of the magnitudes and directions of the rotor angular momentum of the CMGs on the dynamic responses and characteristics of the inflatable space structure.

     

基于液相法二维异质结的空间结构可控制备

The research in two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides (TMDs) and black phosphorus, has been further flourished with the recent emergence of heterostructures composed of dissimilar 2D materials. The interfacing/coupling between different constituent components in a heterostructure has given rise to interesting phenomena and useful properties. For example, depending on the type of 2D materials, the distance and the kind of bonding between them, as well as the crystalline property of the hetero-interface, the interface may provide charge traps, exciton recombination centers, or bridges for effective charge/energy transfer. It has also been found that the spatial arrangement in addition to the composition of the constituents is an important factor influencing the overall properties of the heterostructures. Although many methods, such as dry transfer and vapor-phased growth are able to yield heterostructures from pristine or highly crystalline 2D crystals with spatial control, such as vertical heterostructures and lateral heterostructures, these methods are generally not scalable, which has restricted the use of the obtained heterostructures mostly to fundamental studies. The solution-phased synthesis methods, such as solvothermal/hydrothermal synthesis, electrochemical deposition and hot-injection method, may be more suitable for mass production of functional heterostructures despite the relatively low product quality. In the past couple of years, a diverse kinds of hetero/hybrid structures of 2D materials have been prepared successfully in wet-chemical processes. However, precise control over the geometric arrangement of the constituent components has been challenging in solution. Currently, four types of heterostructures including 2D crystals grown on a larger 2D template, vertical heterostructures, lateral heterostructures, and core-shell heterostructures have been prepared in solution. For the first type, flexible 2D nanosheets such as graphene and monolayer TMDs are used as synthesis templates to support the nucleation and growth of other 2D crystals. For vertical heterostructures, relatively rigid nanoplates are used to allow continuous deposition of 2D layers of other materials to form sandwich-like structures. The formation of lateral heterostructures requires edge growth on existing 2D materials without basal deposition, and therefore other methods such as cation exchange can be used as alternative routes. The preparation of core-shell 2D heterostructures generally involves both epitaxial edge growth and basal deposition and has been realized in both metallic and semiconductor structures. In this review, these kinds of heterostructures based on 2D materials will be discussed in terms of their synthesis methods, properties and possible applications. In addition, we will discuss the challenges and possible opportunities in this research direction.     

Targeting matrix metalloproteinases in acute inflammatory shock syndromes

The integrity of the vascular wall and its intrinsic basement membrane structures ensure that plasma and the corpuscular elements of the blood remain confined to the intravascular milieu and can enter into the extravascular compartment in a well controlled fashion in cases of tissue infection or inflammation. However, sometimes inflammatory stimuli act on blood leukocytes and on endothelial cells from within the blood vessels and in an overwhelming way, leading to inflammatory shock syndromes. These severe conditions with high mortality rates are characterized by intravascular neutrophil degranulation, permeability changes of endothelia and disintegration of basement membranes and lead to almost uncontrollable edema, coagulation changes and multi-organ failure. Matrix metalloproteinases (MMPs) have been functionally linked with septic and endotoxin shock, with cytokine release syndromes and with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Here we review a number of association studies, compare inflammatory shock data from gene knockout studies in mice and provide some insights from recent investigations with inhibitors of MMPs. This evaluation strengthens the expectation that MMP inhibitors, in particular those blocking neutrophil proteases, may become useful in the early phase of acute inflammatory shock syndromes.     

Digital wavelength switching by thermal and carrier injection effects in V-coupled cavity semiconductor laser

Consecutive wavelength switching characteristics of a simple, compact, and digitally wavelength-switchable laser based on V-coupled cavities are reported. Wavelength switching through thermal and carrier injection effects is examined. Without using band gap engineering for the tuning section, 26- and 9-channel wavelength switching schemes are achieved via thermal and carrier injection effects, respectively. The performances of these two tuning schemes are then compared.     

Synthesis of N-confused phlorins via an addition/cyclization pathway

The syntheses of N-confused phlorins are provided by reactions of N-confused porphyrins with nitrilimines and with dialkyl acetylenedicarboxylate. Both reactions involve zwitterionic intermediates and proceed through an addition/cyclization pathway.     

Highly regio- and stereoselective synthesis of tetrasubstituted olefins by the three-component tandem reaction of allylzinc bromide, acetylenic sulfone, and halohydrocarbon

[reation: see text]. Tetrasubstituted olefins containing a 1,4-diene structural unit can be regio- and stereoselectively constructed in one pot by the allylzincation of acetylenic sulfones, followed by Negishi cross-coupling with halohydrocarbons in the presence of catalytic Ni(PPh3)2Cl2.