On the accuracy of micro Winkler titration procedures: a case study

Accuracy data (expressed as precision and trueness) presented by the authors of three different micro modifications of the Winkler titration procedure for dissolved oxygen concentration determination are critically evaluated. Tentative uncertainty estimates are extracted from the data based on the single-laboratory validation approach (originally published in the Nordtest Technical Report 537) and they lead to expanded uncertainty (k = 2) estimates in the range from 0.13 to 0.27 mg l⁻¹ for the three procedures. It is demonstrated that, in all cases, the authors have presented the accuracy and/or precision estimates of the procedures in a way that can lead to too optimistic conclusions about the uncertainty of their procedures. This case study demonstrates the usefulness and flexibility of the single-laboratory validation approach to uncertainty estimation, even in the case of insufficient data, and can be of interest to laboratory workers dealing with measurement procedures from the literature. It is also expected to be of interest to university instructors of analytical chemistry and metrology in chemistry as a real-life example of the critical evaluation of the literature data. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Strong Morita equivalence for ordered semigroups with local units

We prove that partially ordered semigroups with local units are strongly Morita equivalent if and only if they have a joint enlargement, which in turn happens if and only if the Cauchy completions of the semigroups are equivalent.     

Crystal structure of cold compressed graphite

Through a systematic structural search we found an allotrope of carbon with Cmmm symmetry which we predict to be more stable than graphite for pressures above 10 GPa. This material, which we refer to as Z-carbon, is formed by pure sp(3) bonds and it provides an explanation to several features in experimental x-ray diffraction and Raman spectra of graphite under pressure. The transition from graphite to Z-carbon can occur through simple sliding and buckling of graphene sheets. Our calculations predict that Z-carbon is a transparent wide band-gap semiconductor with a hardness comparable to diamond.     

Modeling incoherent reflections from rough room surfaces with image sources

Reflections at rough surfaces change the temporal structure of the reflected signal. This paper shows how to incorporate this temporal behavior in geometric room acoustics modeling. Specifically, a beam tracer is used for calculating the image sources and reflection paths. The roughness of the surfaces is taken into account in post-processing. A single reflection is assumed to distribute the energy according to an exponential function in time based on Biot's rough surface modeling theory. Multiple reflections are modeled with convolutions of exponential functions which are approximated as gamma functions.     

A Thermoanalytical Study of Copper(I) Thiocarbamide Compounds

Hydrated isostructural 1:3 complexes of copper(I) chloride and bromide with thiourea were synthesised and their thermal decomposition studied by simultaneous TG/DTA complemented by ex situ FTIR and XRD studies. The decomposition of Cu(tu)₃Cl·H₂O is initiated by dehydration around 100°C, followed by a total multi-step degradation of the structure in the temperature range of 200–600°C. The counter ion has some influence on the temperatures and composition of the solid residue. The results were compared with those obtained with the 1:1 complex Cu(tu)Cl·1/2H₂O. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of smoothing techniques in the run to run optimization of fed‐batch processes with u‐PLS

Run to run (R2R) optimization based on unfolded Partial Least Squares (u‐PLS) is a promising approach for improving the performance of batch and fed‐batch processes as it is able to continuously adapt to changing processing conditions. Using this technique, the regression coefficients of PLS are used to modify the input profile of the process in order to optimize the yield. When this approach was initially proposed, it was observed that the optimization performed better when PLS was combined with a smoothing technique, in particular a sliding window filtering, which constrained the regression coefficients to be smooth. In the present paper, this result is further investigated and some modifications to the original approach are proposed. Also, the suitability of different smoothing techniques in combination with PLS is studied for both end‐of‐batch quality prediction and R2R optimization. The smoothing techniques considered in this paper include the original filtering approach, the introduction of smoothing constraints in the PLS calibration (Penalized PLS), and the use of functional analysis (Functional PLS). Two fed‐batch process simulators are used to illustrate the results. Copyright © 2015 John Wiley & Sons, Ltd.     

Biosourced All-Acrylic ABA Block Copolymers with Lactic Acid-Based Soft Phase

Lactic acid is one of the key biobased chemical building blocks, given its readily availability from sugars through fermentation and facile conversion into a range of important chemical intermediates and polymers. Herein, well-defined rubbery polymers derived from butyl lactate solvent were successfully prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization of the corresponding monomeric acrylic derivative. Good control over molecular weight and molecular weight distribution was achieved in bulk using either monofunctional or bifunctional trithiocarbonate-type chain transfer agents. Subsequently, poly(butyl lactate acrylate), with a relative low T_g (−20 °C), good thermal stability (5% wt. loss at 340 °C) and low toxicity was evaluated as a sustainable middle block in all-acrylic ABA copolymers using isosorbide and vanillin-derived glassy polyacrylates as representative end blocks. Thermal, morphological and mechanical properties of copolymers containing hard segment contents of <20 wt% were evaluated to demonstrate the suitability of rubbery poly(alkyl lactate) building blocks for developing functional sustainable materials. Noteworthy, 180° peel adhesion measurements showed that the synthesized biosourced all-acrylic ABA copolymers possess competitive performance when compared with commercial pressure-sensitive tapes.     

Characterisation of thin films of ceria-based electrolytes for IntermediateTemperature — Solid oxide fuel cells (IT-SOFC)

At the present, a major technological challenge for the development of solid oxide fuel cells (SOFC) is the reduction of their operation temperature in order to reduce the costs and increase the fuel cell lifetime. Nevertheless, decrease in the operating temperature leads to losses in cell performance mainly due to the ohmic drop through the electrolyte. Therefore, several approaches are currently under investigation to overcome the electrolyte problem and the use of oxygen ion conductor thin films seems to be the most promising solution. In this respect, the well-known electrolyte CeO₂-Gd₂O₃ (CGO) was investigated. Thin layers of less than 5 μm of CGO were deposited using two different techniques: RF magnetron sputtering and Atomic Layer Deposition (ALD). Physicochemical properties of the thin films obtained were characterised by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Furthermore, impedance measurements were carried out in order to determine the electrical properties of the CGO films, in particular their ionic conductivity. Paper presented at the 9th EuropConference on Ionics, Ixia, Rhodes, Greece, Sept. 15–21, 2002.