BMO and uniform estimates for multi-well problems

We establish optimal local regularity results for vector-valued extremals and minimizers of variational integrals whose integrand is the squared distance function to a compact set K in matrix space ${{{\mathbb M}^{N \times n}}}$ . The optimality is illustrated by explicit examples showing that, in the nonconvex case, minimizers need not be locally Lipschitz. This is in contrast to the case when the set K is suitably convex, where we show that extremals are locally Lipschitz continuous. The results rely on the special structure of the integrand and elementary Cordes–Nirenberg type estimates for elliptic systems.     

Benchmark density functional theory calculations for nanoscale conductance

We present a set of benchmark calculations for the Kohn-Sham elastic transmission function of five representative single-molecule junctions. The transmission functions are calculated using two different density functional theory methods, namely an ultrasoft pseudopotential plane-wave code in combination with maximally localized Wannier functions and the norm-conserving pseudopotential code SIESTA which applies an atomic orbital basis set. All calculations have been converged with respect to the supercell size and the number of k|| points in the surface plane. For all systems we find that the SIESTA transmission functions converge toward the plane-wave result as the SIESTA basis is enlarged. Overall, we find that an atomic basis with double zeta and polarization is sufficient (and in some cases, even necessary) to ensure quantitative agreement with the plane-wave calculation. We observe a systematic downshift of the SIESTA transmission functions relative to the plane-wave results. The effect diminishes as the atomic orbital basis is enlarged; however, the convergence can be rather slow.     

THM PyGC–MS of wood fragment and vegetable fibre forensic samples

Wood fragments and vegetable fibres were investigated using thermally assisted hydrolysis and methylation with pyrolysis gas chromatography–mass spectrometry (THM PyGC–MS). Multiple ion chromatography was used to decrease the interference from cellulosic peaks, and to obtain greater resolution between the lignin peaks. Forty-four wood samples were analysed using THM PyGC–MS. The wood fragments were able to be differentiated into angiosperms (hardwoods) and gymnosperms (softwoods) using principle component analysis (PCA), hierarchical cluster analysis (HCA), and the ratio of syringyl to guaiacyl lignin fragments (S/G ratio). PCA and HCA also differentiated several Monterey pine samples from the rest of the gymnosperms, primarily by the presence of β-pinene, an extractive compound. Other gymnosperm species and the individual angiosperm species were unable to be differentiated. A pilot study investigating the use of THM PyGC–MS for the analysis of vegetable fibres in forensic science found that the fibre types tended to group into two clusters, with one containing cotton, hemp and linen; and the other consisting of hessian, sisal, jute and coir. The seagrass sample was able to be differentiated from both groups. These groups were well separated using PCA, HCA and by the ratio of cinnamyl phenolic derivatives to guaiacyl lignin derivatives (C/G ratio). Some grouping of each fibre type was evident within each cluster, however the separation between the clusters was insufficient to differentiate them using these statistical techniques. THM PyGC–MS of vegetable fibres showed some potential for future use in forensic science.     

Synthesis of substituted 2-cyanoarylboronic esters

The synthesis of substituted 2-cyanoarylboronic esters is described via lithiation/in situ trapping of the corresponding methoxy-, trifluoromethyl-, fluoro-, chloro-, and bromobenzonitriles. The crude arylboronic esters were obtained in high yields and purities and with good regioselectivities.     

Direct Cu-mediated aromatic 18F-labeling of highly reactive tetrazines for pretargeted bioorthogonal PET imaging

Pretargeted imaging can be used to visualize and quantify slow-accumulating targeting vectors with short-lived radionuclides such as fluorine-18 – the most popular clinically applied Positron Emission Tomography (PET) radionuclide. Pretargeting results in higher target-to-background ratios compared to conventional imaging approaches using long-lived radionuclides. Currently, the tetrazine ligation is the most popular bioorthogonal reaction for pretargeted imaging, but a direct ¹⁸F-labeling strategy for highly reactive tetrazines, which would be highly beneficial if not essential for clinical translation, has thus far not been reported. In this work, a simple, scalable and reliable direct ¹⁸F-labeling procedure has been developed. We initially studied the applicability of different leaving groups and labeling methods to develop this procedure. The copper-mediated ¹⁸F-labeling exploiting stannane precursors showed the most promising results. This approach was then successfully applied to a set of tetrazines, including highly reactive H-tetrazines, suitable for pretargeted PET imaging. The labeling succeeded in radiochemical yields (RCYs) of up to approx. 25%. The new procedure was then applied to develop a pretargeting tetrazine-based imaging agent. The tracer was synthesized in a satisfactory RCY of ca. 10%, with a molar activity of 134 ± 22 GBq μmol⁻¹ and a radiochemical purity of >99%. Further evaluation showed that the tracer displayed favorable characteristics (target-to-background ratios and clearance) that may qualify it for future clinical translation.

A simple, scalable and reliable direct ¹⁸F-labeling procedure has been developed and applied to obtain a pretargeting tetrazine-based imaging agent with favorable in vivo characteristics.     

All-silica nanofluidic devices for DNA-analysis fabricated by imprint of sol-gel silica with silicon stamp

We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination of the imprinted hybrid sol-gel material produces purely inorganic silica, which has very low autofluorescence and can be fusion bonded to a glass lid. Compared to top-down processing of fused silica or silicon substrates, imprint of sol-gel silica enables fabrication of high-quality nanofluidic devices without expensive high-vacuum lithography and etching techniques. The applicability of the fabricated device for single-molecule studies is demonstrated by measuring the extension of DNA molecules of different lengths confined in the nanochannels.     

High resolution inductively coupled plasma mass spectrometry (HR-ICPMS) determination and multivariate evaluation of 10 trace elements in mussels from 7 sites in Limfjorden, Denmark

The contents of V, Cr, Co, Ni, Cu, Ga, Rb, Cd, Ba, and Pb in the soft tissue of blue mussel (Mytilus edulis) were determined by a high resolution inductively coupled plasma mass spectrometry (HR-ICPMS) method. Sample digestions were performed in closed microwave vessels using nitric acid and hydrogen peroxide. Using HR-ICPMS it is possible to resolve the analytical peaks from otherwise interfering polyatomic ions with a mass resolution setting of 4000 (Cr, Ni, Cu). The proposed method was validated using a mussel tissue reference material (NIST SRM 2974). The proposed method was applied to real samples of blue mussel from seven sites in the inlet “Limfjorden”, Denmark, and the levels of trace elements found were compared with the levels found in an earlier study. For the mussel samples large inter-regional differences in trace element concentrations in the tissues were recorded. The mussels from the different sites could be separated using principal component analysis (PCA). Comparison with the levels of trace elements in mussels found in 1982 showed that the trace elemental contamination has increased during the last 15 years. From the data obtained, mussel tissue appears to be good bio-indicator for identification of coastal areas exposed to metallic contaminants.     

Determination of SFC, FFA, and equivalent reaction time for enzymatically interestified oils using NIRS

The use of near infrared spectroscopy (NIRS) for rapid determination of the degree of interesterification of blends of palm stearin, coconut oil, and rapeseed oil obtained using an immobilized Thermomyces lanuginosa lipase at 70 °C was investigated. Interesterification was carried out by applying both fixed bed and batch reactors. Calibrations were developed for quantitative determination of solid fat content (SFC) at 10, 20, 30, 35, and 40 °C and free fatty acid (FFA) resulting in root mean square errors of prediction of 1.0, 1.3, 1.4, 1.6, 1.7, and 0.19% (w/w), respectively. The data showed that NIRS could be used to replace the traditional methods for determining FFA and SFC in vegetable oils.It was possible to monitor the activity of the immobilized enzyme for interesterification of margarine oils by predicting the equivalent reaction time in a batch reactor from NIR spectra. Root mean square errors of prediction for two different oil blends interesterified for 300 and 170 min were 21 and 12 min, respectively.