Few‐Layer Black Phosphorus Carbide Field‐Effect Transistor via Carbon Doping

Black phosphorus carbide (b‐PC) is a new family of layered semiconducting material that has recently been predicted to have the lightest electrons and holes among all known 2D semiconductors, yielding a p‐type mobility (≈10⁵ cm² V^?1 s^?1) at room temperature that is approximately five times larger than the maximum value in black phosphorus. Here, a high‐performance composite few‐layer b‐PC field‐effect transistor fabricated via a novel carbon doping technique which achieved a high hole mobility of 1995 cm² V^?1 s^?1 at room temperature is reported. The absorption spectrum of this material covers an electromagnetic spectrum in the infrared regime not served by black phosphorus and is useful for range finding applications as the earth atmosphere has good transparency in this spectral range. Additionally, a low contact resistance of 289 Ω µm is achieved using a nickel phosphide alloy contact with an edge contacted interface via sputtering and thermal treatment.     

Stable Molecular Diodes Based on π–π Interactions of the Molecular Frontier Orbitals with Graphene Electrodes

In molecular electronics, it is important to control the strength of the molecule–electrode interaction to balance the trade‐off between electronic coupling strength and broadening of the molecular frontier orbitals: too strong coupling results in severe broadening of the molecular orbitals while the molecular orbitals cannot follow the changes in the Fermi levels under applied bias when the coupling is too weak. Here, a platform based on graphene bottom electrodes to which molecules can bind via π–π interactions is reported. These interactions are strong enough to induce electronic function (rectification) while minimizing broadening of the molecular frontier orbitals. Molecular tunnel junctions are fabricated based on self‐assembled monolayers (SAMs) of Fc(CH₂)₁₁X (Fc = ferrocenyl, X = NH₂, Br, or H) on graphene bottom electrodes contacted to eutectic alloy of gallium and indium top electrodes. The Fc units interact more strongly with graphene than the X units resulting in SAMs with the Fc at the bottom of the SAM. The molecular diodes perform well with rectification ratios of 30–40, and they are stable against bias stressing under ambient conditions. Thus, tunnel junctions based on graphene with π–π molecule–electrode coupling are promising platforms to fabricate stable and well‐performing molecular diodes.     

Nanoparticle Interactions Guided by Shape‐Dependent Hydrophobic Forces

Self‐assembly of solvated nanoparticles (NPs) is governed by numerous competing interactions. However, relatively little is known about the time‐dependent mechanisms through which these interactions enable and guide the nanoparticle self‐assembly process. Here, using in situ transmission electron microscopy imaging combined with atomistic modeling, it is shown that the forces governing the self‐assembly of hydrophobic nanoparticles change with the nanoparticle shapes. By comparing how gold nanospheres, nanocubes, nanorods, and nanobipyramids assemble, it is shown that the strength of the hydrophobic interactions depends on the overlap of the hydrophobic regions of the interacting nanoparticle surfaces determined by the nanoparticle shapes. Specifically, this study reveals that, in contrast to spherical nanoparticles, where van der Waals forces play an important role, hydrophobic interactions can be more relevant for nanocubes with flat side faces, where an oriented attachment between the nanocubes is promoted by these interactions. The attachment of nanocubes is observed to proceed in two distinct pathways: nanocubes either: (i) prealign their faces before the attachment, or (ii) first connect through a misaligned (edge‐to‐edge) attachment, followed by a postattachment alignment of their faces. These results have important implications for understanding the interaction dynamics of NPs and provide the framework for the design of future self‐assembled nanomaterials.     

Engineering of the substrate-binding region of the sublilisin-like, cell-envelop proteinase of Lactococcus lactis

The substrate-binding region of the cell-envelope proteinaseof Lactococcus lactis strain SK11 was modelled, based on sequencebomology of the catalytic domain with the serine proteinasessubtilisin and thermitase. Substitutions, deletions and insertionswere introduced, by site-directed and cassette mutagenesfe ofthe prtP gene encoding this enzyme, based on sequence comparisonboth with subtilisin and with the homologous L.lactis strainWg2 proteinase, which has different proteolytic properties.The engineered enzymes were investigated for thermal stability,proteolytic activity and cleavage specificity towards smallchromogenk peptide substrates and the peptide _g1-casein(l–23).Mutations in the subtilisin-like substrate-binding region showedthat Ser433 is the active site residue, and that residues 138and 166 at either side of the binding cleft play an importantrole in substrate specificity, particularly when these residuesand the substrate are oppositely charged. The K748T mutationin a different domain also affected specificity and stability,suggesting that this residue is in close proximity to the subtilisin-likedomain and may form part of the substratebinding site. Severalmutant SK11 proteinases have novel properties not previouslyencountered in natural variants. Replacements of residues 137–139AKTalong one side of the binding cleft produced the 137–139GPPmutant proteinase with reduced activity and narrowed specificity,and the 137–139GLA mutant with increased activity andbroader specificity. Furthermore, the 137–139GDT mutanthad a specificity towards _g1,-casein(l–23) closely resemblingthat of L.lactis Wg2 proteinase. Mutants with an additionalnegative charge in the binding region were more stable towardsautoproteolysis.     

Cloning, characterization and expression of a calnexin homologue from the pathogenic fungus Paracoccidioides brasiliensis

We report the cloning of a Paracoccidioides brasiliensis cDNA, here named PbCnx, encoding the homologue of the endoplasmic reticulum molecular chaperone calnexin. Calnexin specifically recognizes monoglucosylated glycoproteins in the endoplasmic reticulum, thus being an essential component of the complex that interacts with the folded state of nascent secreted glycoproteins. The PbCnx open reading frame was found in a 1701 base pair (bp) fragment that encodes a 567 amino acid protein with an estimated mass of 62 680 Da. Northern and Southern blot hybridizations showed that PbCnx is encoded by a single, or a low number of, gene copies. PbCnx contains the hallmark KPEDWD motifs that are found in all members of the calnexin/calreticulin family proteins. A cDNA-encoding PbCnx was overexpressed as recombinant protein in Escherichia coli. The purified recombinant PbCnx was recognized by 6 out of 10 sera from PCM patients, a result that rules out its possible consideration for further use in diagnosis. Using confocal microscopy with anti-PbCnx mouse serum against yeast forms, a cytoplasmic staining pattern was observed.     

城市荒野景观及其营造策略：以荷兰 实践为例

在国际范围内荒野保护运动持续发展的同时,中国 的荒野保护体系正在稳步建立。但随着城市化进程的不断加 速,城市中自然荒野空间的开发是不可避免的。如何在不断扩 张的城市范围内尽可能保留与规划荒野景观,已经成为国内风 景园林设计师关注的问题。在梳理了城市荒野课题相关背景和 研究进展后,探索了荷兰的城市荒野实践经验,并选取3个不 同尺度和类型的代表性案例,分别对案例的项目背景、设计要 点和场地功能进行研究分析,进而提出自然优先、野性保护、 控制扰动和公众参与4点原则,并辩证地提取了可指导中国背 景下不同尺度城市荒野景观营造的策略,为构建中国荒野体系 提供了国际经验。     

Esterification in a structured catalytic reactor with counter-current water removal

In this research the liquid phase esterification of hexanoic acid and 1-octanol was studied. Very high activities were obtained for zeolite BEA and Nafion/silica composite with 13% of Nafion. The advantage of water removal in this system was demonstrated. In a closed system an equilibrium conversion of 35% was reached, while in a system with water removal all the reactants were converted in a shorter period. The initial reaction rate decreases when increasing the initial water concentration, following a Langmuir–Hinshelwood type of rate expression. An active zeolite coated structured monolithic reactor configuration was prepared. Enhancement by the counter-current water stripping of the performance of the structured catalysts was demonstrated.     

三角洲适应性转型——基于景观的区域设计方法

针对气候变化和城市化对富饶的三角洲地区带来的洪涝风险、生态、社会—文化价值流失等威胁,提出将三角洲城市化进程视为一系列具有独立动态特征和速率变化的复杂社会—生态系统(子系统),急需为保障该类型区域的可持续发展提供空间战略,以协助修复系统漏洞并增强应对自然和人工威胁的能力,以珠江三角洲为例,针对城市化进程中三角洲区域的适应性城市转型,提出基于景观的区域设计方法。通过对自然和城市景观要素转型性循环的各类动态变化进行评估,得到生态动力型区域设计战略,为城市化进程中的自然和社会—文化发展提供更多机遇。提出保障水安全和全纳性社会—生态设计的适应性转型视角。