Chiral semiconductor phases: the optically pure D3[M(III)(S,S-EDDS)]2 (D=TTF, TSF) family

A new family of optically pure tetrathiafulvalenium and tetraselenafulvalenium salts, D(3)[M(III)(S,S-EDDS)](2)·nH(2)O (where D = TTF, TSF; M = Co, Fe, Cr; EDDS = ethylenediaminedisuccinato), were synthesized electrochemically. These phases are semiconductors with conductivities between 6.9 × 10(-6) and 1.3 × 10(-5) S·cm(-1) (E(a)ca. 0.3 eV) for TTF and 2.8 × 10(-4) to 2.8 × 10(-5) S·cm(-1) (E(a)ca. 0.1 eV) for TSF compounds. While some crystals suffer from twinning, other well resolved structures consist of TTF/TSF stacks which, under the influence of the chiral anion, exhibit a periodic undulation described by an elliptical helix. The crystallographic data, along with computational work, indicate charge localization in the semiconducting motifs.     

The chemistry and complexes of small cyano anions

The chemistry of the anions dicyanamide and tricyanomethanide (dca and tcm, respectively) has produced a plethora of discoveries over the past few decades, particularly in relation to transition-metal coordination polymers with magnetic coupling. Over recent years there have been an increasing number of reports of heterofunctionalised cyano-containing anions, typically derivatives of dicyanomethanide. Our own group has been particularly concerned with the amide- and nitroso-functionalised anions carbamoyldicyanomethanide (cdm) and dicyanonitrosomethanide (dcnm), respectively. This feature article examines the fascinating diversity of materials and complexes that can be obtained using small cyano anions, ranging from coordination polymers to heterometallic clusters and hydrogen bonding networks. In particular, we focus on results from our own laboratories in the past few years. The magnetic properties of these materials are briefly discussed.     

Isomeric Fe(II) MOFs: from a diamond-framework spin-crossover material to a 2D hard magnet

Two Fe(II) coordination polymers formed from isomeric ligands give a diamond-like 3D network exhibiting a gradual SCO and a 2D hard magnet with a large coercive field.     

On generalized balanced optimization problems

In the generalized balanced optimization problem (GBaOP) the objective value \({\max_{e \in S}{|c(e)-k\max(S)|}}\) is minimized over all feasible subsets S of E = {1, . . . , m}. We show that the algorithm proposed in Punnen and Aneja (Oper Res Lett 32:27–30, 2004) can be modified to ensure that the resulting solution is indeed optimal. This modification is attained at the expense of increased worst-case complexity, but still maintains polynomial solvability of various special cases that are of general interest. In particular, we show that GBaOP can be solved in polynomial time if an associated bottleneck problem can be solved in polynomial time. For the solution of this bottleneck problem, we propose two alternative approaches.     

A study of early career teachers’ practices related to language and language diversity during mathematics instruction

The role of language in mathematics teaching and learning is increasingly highlighted by standards and reform movements in the US. However, little is known about teachers’, and especially early career teachers’ (ECTs) practices and understandings related to language in mathematics instruction. This multiple case study explored the language-related understandings and practices of six ECTs in diverse elementary classrooms. Using iterative cycles of analysis, we found that all ECTs regularly attended to students’ mathematical vocabulary use and development. Yet, there was variability in ECTs’ focus on how to teach mathematical vocabulary, expectations for students’ precise use of mathematical terminology, and the use of multiple languages during instruction. These findings indicate that ECTs need more targeted support during teacher preparation and early career teaching in order to better support all students’ language development in the mathematics classroom.     

Ruthenized screen-printed choline oxidase-based biosensors for measurement of anticholinesterase activity

Plastic disposable choline biosensors based on ruthenized-carbon screen-printed electrodes were prepared and their use for monitoring organophosphorus pesticides and carbamates is described. The presence of 0.5% ruthenium on activated carbon mixed to form a simple graphite-based ink for the working electrode surface increased the sensitivity towards hydrogen peroxide. The choline biosensor is based on such an electrode coupled with choline oxidase immobilized by adsorption and was used to detect the inhibition effect of carbamates and organophosphorus pesticides on acetylcholinesterase. With the optimized procedure described (pH, buffer composition, incubation time, substrate concentration), concentrations of pesticides (Carbofuran) as low as 1 nM could be detected.     

互补对偶结构的三值ECL锁存器设计

在分析发射极耦合逻辑(ECL)电路的互补对偶特性基础上,指出了差分对的两个开关变量的不独立性及互补对偶特性,并设计了互补对偶结构的ECL三值D型锁存器.这种新型的D型锁存器电路比传统电路具有更简单的电路结构.它的输出是互补的双轨三值输出系统.应用这种新型锁存器设计的D触发器及时序电路将具有更简单的电路结构.     

An inter-comparison of far-infrared line-by-line radiative transfer models

A considerable fraction (>40%) of the outgoing longwave radiation escapes from the Earth's atmosphere-surface system within a region of the spectrum known as the far-infrared (wave-numbers less than 650 cm⁻¹). Dominated by the line and continuum spectral features of the pure rotation band of water vapor, the far-infrared has a strong influence upon the radiative balance of the troposphere, and hence upon the climate of the Earth. Despite the importance of the far-infrared contribution, however, very few spectrally resolved observations have been made of the atmosphere for wave-numbers less than 650 cm⁻¹. The National Aeronautics and Space Administration (NASA), under its Instrument Incubator Program (IIP), is currently developing technology that will enable routine, space-based spectral measurements of the far-infrared. As part of NASA's IIP, the Far-Infrared Spectroscopy of the Troposphere (FIRST) project is developing an instrument that will have the capability of measuring the spectrum over the range from 100 to 1000 cm⁻¹ at a resolution of 0.6 cm⁻¹. To properly analyze the data from the FIRST instrument, accurate radiative transfer models will be required. Unlike the mid-infrared, however, no inter-comparison of codes has been performed for the far-infrared. Thus, in parallel with the development of the FIRST instrument, an investigation has been undertaken to inter-compare radiative transfer models for potential use in the analysis of far-infrared measurements. The initial phase of this investigation has focused upon the inter-comparison of six distinct line-by-line models. The results from this study have demonstrated remarkably good agreement among the models, with differences being of order 0.5%, thereby providing a high measure of confidence in our ability to accurately compute spectral radiances in the far-infrared.