Halogen bonding: Recent advances

Halogen bonding (XB), as a directional interaction between covalently bound halogen atoms (XB donor) and Lewis bases (A, XB acceptor), has been recently intensively investigated as a powerful tool in crystal engineering. After a short review on the origin and general features of halogen bonding, current developments towards (i) the elaboration of three-dimensional networks, (ii) the interaction with anionic XB acceptors, (iii) its identification in biological systems and (iv) the formation of liquid crystal phases will be described. Theoretical analyses, statistical studies and experimental electron density determinations converge to describe halogen bonding as a relatively weak structure directing tool, when compared with hydrogen bonding. However, when the halogen atom is strongly activated as in iodoperfluorinated molecules or cationic aromatic systems can halogen bonding act as an efficient and reliable structure directing tool.     

Megasonic agitation for enhanced electrodeposition of copper

In this paper we propose an agitation method based on megasonic acoustic streaming to overcome the limitations in plating rate and uniformity of the metal deposits during the electroplating process. Megasonic agitation at a frequency of 1 MHz allows the reduction of the thickness of the Nernst diffusion layer to less than 600 nm. Two applications that demonstrate the benefits of megasonic acoustic streaming are presented: the formation of uniform ultra-fine pitch flip-chip bumps and the metallisation of high aspect ratio microvias. For the latter application, a multi-physics based numerical simulation is implemented to describe the hydrodynamics introduced by the acoustic waves as they travel inside the deep microvias.     

Zn in Athenian Black Gloss Ceramic Slips: A Trace Element Marker for Fabrication Technology

The black‐colored pottery slips produced in Athens from the 6th to 4th centuries B.C., had a consistent composition achieved through processing and refinement of raw clay. Little direct evidence has been established as to what were these refinement methods. To better understand how the slip material was prepared, the major and trace elemental compositions of 19 slips from different ceramic vessels and their corresponding bodies of Athenian red‐figure and black‐figure vases were determined using laser ablation inductively coupled plasma mass spectrometry (LA‐ICPMS). Notably higher Zn concentrations were found in the slips (271–1959 ppm) than in their corresponding body ceramics (<361 ppm). The Zn concentrations in the slips were also found to be above the natural background for typical clay (between 10 and 300 ppm) suggesting an unintentional anthropogenic enrichment of this metal. Based on the abnormally high Zn content of the slip, it is speculated that the clay was treated using vitriol (concentrated acid mine runoff which is rich in Zn), to induce flocculation and remove carbonate mineral phases from the raw material that, if present, would prevent the slip from vitrifying. This same signature of elevated levels of Zn with a corresponding Ce anomaly is also observed for black glosses produced in Corinthian and Etrurian (Italy) workshops indicating that these trace element signatures were imparted to the material by means of shared methods of manufacturing instead of being indicative of a single unique source for this material.     

Some Sources of Residential Satisfaction in an Urban Slum

Urban renewal planning has assumed that social benefits would accrue to the former residents of slums. But the meanings that the slum areas have for their residents and the consequent effects that relocation would have for them have not been adequately understood. Prior to being located from Boston's West End redevelopment area, most residents experienced profound satisfaction from living in the area. Their satisfaction derived, in large part, from the close associations maintained among the local people and from their strong sense of identity to the local places. In turn, people and places provided a framework for personal and social integration.     

Modern landscape architecture: monuments and icons

In November, 2005, The Journal of Architecture (Volume 10, Number 5) published Criticality in between China and the West by Jianfei Zhu: there followed extensive critical responses to this paper (on the architectural web in China; an extended seminar was held at Tongji University) which are detailed at the end of this section. Published here are two commentaries submitted to The Journal of Architecture, Tao Zhu's in direct response to the original essay, and Jianfei Zhu's response to Tao Zhu.     

Methodology for quantifying the volatile mixing state of an aerosol

Mixing state refers to the relative proportions of chemical species in an aerosol, and the way these species are combined; either as a population where each particle consists of a single species (‘externally mixed’) or where all particles individually consist of two or more species (‘internally mixed’) or the case where some particles are pure and some particles consist of multiple species. The mixing state affects optical and hygroscopic properties, and quantifying it is therefore important for studying an aerosol's climate impact. In this article, we describe a method to quantify the volatile mixing state of an aerosol using a differential mobility analyzer, centrifugal particle mass analyzer, catalytic denuder, and condensation particle counter by measuring the mass distributions of the volatile and non-volatile components of an aerosol and determining how the material is mixed within and between particles as a function of mobility diameter. The method is demonstrated using two aerosol samples from a miniCAST soot generator, one with a high elemental carbon (EC) content, and one with a high organic carbon (OC) content. The measurements are presented in terms of the mass distribution of the volatile and non-volatile material, as well as measures of diversity and mixing state parameter. It was found that the high-EC soot nearly consisted of only pure particles where 86% of the total mass was non-volatile. The high-OC soot consisted of either pure volatile particles or particles that contained a mixture of volatile and non-volatile material where 8% of the total mass was pure volatile particles and 70% was non-volatile material (with the remaining 22% being volatile material condensed on non-volatile particles).

© 2016 American Association for Aerosol Research     

Magnetically controlled shape-memory effects of hybrid nanocomposites from oligo(ω-pentadecalactone) and covalently integrated magnetite nanoparticles

The covalent integration of inorganic nanoparticles in polymer matrices has gained significance for improving the structural properties of polymer-based materials. Here we report on the performance of poly(ω-pentadecalactone) networks with magnetite nanoparticles as netpoints in their magnetically-controlled shape-memory capability. Hybrid nanocomposites with magnetite nanoparticle content ranging from 5 to 11 wt% were prepared by reacting two types of oligo(ω-pentadecalactone) (OPDL) based precursors with terminal hydroxy groups, a three arm OPDL (³AOPDL, M_n = 6000 g mol⁻¹) and an OPDL (M_n = 3300 g mol⁻¹) coated magnetite nanoparticle (∅ = 10 nm), with a diisocyanate. Homogenous hybrid nanocomposites were obtained independent from the weight content of the OPDL decorated nanoparticles in the samples. At 100 °C (T > T_m-OPDL) the covalent integration of the nanoparticles increased the mechanical strength with increasing weight content whereby the elasticity remained almost constant. In magnetically-controlled one-way dual-shape experiments the shape fixity decreased from 95% to 90% but the shape recovery increased slightly from 95% to 97% when the nanoparticle content was increased. In magnetically-controlled reversible dual-shape experiments the nanoparticles had a restraining effect and the maximum shape-change of 65% for hybrid nanocomposites with 5 wt% magnetite nanoparticles was reduced to 36% when the particle content was increased to 11 wt%. These results show that the performance of hybrid nanocomposites can be tailored by nanoparticle content, however in terms of their applicability either mechanical strength or actuation capability should be focussed in the material selection.