Application of main component fraction collection method for purification of compound libraries

In order to support high-throughput library purification, a novel UV triggered fraction collection method was developed in which a maximum-seeking-algorithm-driven, six-port valve collects the largest chromatographic peak. This straightforward strategy achieves the one sample-one fraction approach, thus resulting in a simpler and less error prone workup procedure. The effectiveness of this main component fraction collection method will be illustrated here by the results of the purification of compound libraries (altogether 6086 compounds, having an averaged success rate of 79.4%). Advanced applications, where the desired component differs from the main component, will also be discussed.     

Intravenous administration of Gd-DTPA prior to DWI does not affect the apparent diffusion constant

MRI measurements of water diffusion and blood perfusion are increasingly used for the evaluation of organ functionality and tissue viability (e.g., in tumors). While diffusion-weighted imaging is performed without contrast agents, measurement of blood perfusion is normally performed based on the administration of paramagnetic substances such as gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Simultaneous measurements of these two parameters are often preferred. However, it may be argued that Gd-DTPA causes constriction of small blood vessels or alters hemodynamic parameters such as blood viscosity, thereby corrupting subsequent measurements of the apparent diffusion constant (ADC). The objective of the current study was to investigate the possible changes in the ADC in tumors following intravenous administration of 0.2 and 0.4 mmol/kg of Gd-DTPA in mice. The study was conducted with C3H mouse mammary carcinomas inoculated in the right foot of the animal subjects. The results were compared with findings in a sham group, demonstrating that Gd-DTPA had no significant impact on the ADC as measured in a 7-T animal system.     

Low-cost,solution processable carbon nanotube supercapacitors and their characterization

We report ecological and low-cost carbon nanotube (CNT) supercapacitors fabricated using a simple, scalable solution processing method, where the use of a highly porous and electrically conductive active material eliminates the need for a current collector. Electrodes were fabricated on a poly(ethylene terephthalate) substrate from a printable multi-wall CNT ink, where the CNTs are solubilized in water using xylan as a dispersion agent. The dispersion method facilitates a very high concentration of CNTs in the ink. Supercapacitors were assembled using a paper separator and an aqueous NaCl electrolyte and the devices were characterized with a galvanostatic discharge method defined by an industrial standard. The capacitance of the \(2\hbox { cm}^2\) devices was \(6\hbox { mF/cm}^2\)  (2.3 F/g) and equivalent series resistance \(80\,\Omega \) . Low-cost supercapacitors fabricated from safe and environmentally friendly materials have potential applications as energy storage devices in ubiquitous and autonomous intelligence as well as in disposable low-end products.     

The displacement correlation tensor: microstructure, ensemble anisotropy and curving fibers

Experiments with multiple diffusion wave vectors are known to carry more information than what is available from standard diffusion experiments. Here we consider a special case of this class of pulse sequences, the double wave vector diffusion experiment, and use the cumulant expansion of the signal to introduce the displacement correlation tensor. We discuss its physical interpretation and properties, noting in particular that its short time behavior allows determination of the surface to volume ratio of the pore space. We present a general expression for the displacement correlation tensor, and provide explicit expressions for a few model geometries. We then show that the scatter matrix characterizing the orientation distribution of an ensemble of cylinders is simply related to the displacement correlation tensor. This result is generalized to ensembles of pores with arbitrary shapes allowing a precise formulation of the influence of microstructural and ensemble anisotropy on the double wave vector diffusion signal in the Gaussian phase approximation. Finally, as a new application of the double wave vector diffusion signal, we analyze its behavior in a curving fiber, and suggest that the displacement correlation tensor may be used to estimate sub-voxel fiber curvature and deflection angle. The theoretical results are corroborated by computer simulations.     

UV-triggered main-component fraction collection method and its application for high-throughput chromatographic purification of combinatorial libraries

A maximum-seeking, algorithm-driven fraction collection method was developed to support high-throughput chromatographic purification, which provides new possibilities for off-line high-performance liquid chromatography mass spectroscopy (HPLC/MS) quality control experiments. The method is based on manipulation of a six-port valve that is installed downstream from the UV detector and equipped with a fraction collector loop. The detector signal is monitored by a programmable microcontroller that controls the state of the fraction collector valve. After detecting a chromatographic peak, the appropriate fraction is stored in the collector loop. The height of the next peak is compared to the previous one (using a maximum-seeking algorithm) and, depending on the result, the collected fraction is or is not exchanged with the new one. At the end of the run, the stored UV main component is pumped into the external fraction vial. This configuration was used for chromatographic purification of large compound libraries (the results of the purification of 5324 compounds are reported here), as well as for high-throughput off-line HPLC quality control experiments, where the collected main component fractions of an analytical-scale separation were subjected to further mass spectrometric molecular weight verification.     

Measurement setup for differential spectral responsivity of solar cells

Optical Review - We have developed a setup for measuring differential spectral responsivities of unifacial and bifacial solar cells under bias light conditions. The setup uses 30 high-brightness...     

Characterizing a UV chamber with mercury lamps for assessment of comparability to natural UV conditions

UV radiation conditions in a UV chamber equipped with four 300-W mercury vapour lamps have been characterized to assess the exposure received by the specimens aged in the chamber. Spectrally resolved measurements were performed on UV radiation emitted by new lamps and lamps operated for 4850 h in the chamber. An intensity decrease of as much as 75% with a strong wavelength dependency was detected. By linking the measurements with independent broadband measurements of the UV radiation field emitted by a single lamp, the UV dose rate distribution on the specimen plane of the chamber was derived. A method for true exposure accumulation estimation, accounting for the fading of the lamps, was developed. Accumulated UV radiation exposures on material samples in the chamber were derived and compared to long-term (1995–2007) average UV exposures received in natural sunshine at Jokioinen, Finland (lat. 60.4°N, long. 23.5°E, 104 m a.s.l.). Acceleration factors for the exposure in the UV chamber were derived in terms of doses integrated over different wavelength ranges. The acceleration factor was found to depend strongly on the wavelength range of the dose considered, presenting an extra challenge to the assessment of the artificial material exposure duration.