Electrostatic purification of insulating liquids

Summary A development of the Cottrell filter for the purification of insulating liquids will be described. The original filter for gases has been improved and a more complete theory of the filtration process for insulating liquids has been calculated. It is shown that the theory of high field particle motion in insulating media should be modified for the application at low field strengths and in ionogenic media, where the counter ion atmospheres absorbed to the particles decrease the particle charges.     

Detection and characterization of prednisolone metabolites in human urine by LC‐MS/MS

Glucocorticosteroids are prohibited in sports when used by systemic administrations (e.g. oral), whereas they are allowed using other administration ways. Strategies to discriminate between administrations routes have to be developed by doping control laboratories. For this reason, the metabolism of prednisolone (PRED) was studied using liquid chromatography coupled to tandem mass spectrometry. A single oral (10 mg) dose of PRED was administered to two healthy male volunteers. Urine samples were collected up to 6 days after administration. Samples were hydrolyzed with β‐glucuronidase and subjected to liquid–liquid extraction with ethyl acetate in alkaline conditions. The extracts were analyzed by liquid chromatography coupled to tandem mass spectrometry. Precursor ion scan methods (m/z 77, 91, 105, 121, 147 and 171) in positive ionization and neutral loss scan methods (76 and 94 Da) in negative ionization modes were applied for the open detection of PRED metabolites. Using these methods, PRED parent compound plus 20 metabolites were detected. PRED and 11 metabolites were characterized by comparison with standards of the compounds (PRED, prednisone, 20β‐dihydro‐PRED and 20α‐dihydro‐PRED, 20β‐dihydro‐prednisone and 20α‐dihydro‐prednisone, 6β‐hydroxy‐PRED and 6α‐hydroxy‐PRED, 20β isomers and 20α isomers of 6β,11β,17α,20,21‐pentahydroxypregnan‐1,4‐diene‐3‐one, 6α,11β,17α,20β,21‐pentahydroxypregnan‐1,4‐diene‐3‐one and Δ⁶‐PRED). Using mass spectrometric data, feasible structures were proposed for seven of the remaining nine detected metabolites, including several 6‐hydroxy‐metabolites. Eleven of the characterized metabolites have not been previously described. Maximum excretion rates for PRED metabolites were achieved in first 24 h; however, most of the metabolites were still detectable in the last collected samples (day 6). Copyright © 2015 John Wiley & Sons, Ltd.     

Protonation state of the Cu4S2 CuZ site in nitrous oxide reductase: redox dependence and insight into reactivity

Spectroscopic and computational methods have been used to determine the protonation state of the edge sulfur ligand in the Cu₄S₂ Cu_Z form of the active site of nitrous oxide reductase (N₂OR) in its 3Cu^ICu^II (1-hole) and 2Cu^I2Cu^II (2-hole) redox states. The EPR, absorption, and MCD spectra of 1-hole Cu_Z indicate that the unpaired spin in this site is evenly delocalized over Cu_I, Cu_II, and Cu_IV. 1-hole Cu_Z is shown to have a μ₂-thiolate edge ligand from the observation of S–H bending modes in the resonance Raman spectrum at 450 and 492 cm^–1 that have significant deuterium isotope shifts (–137 cm^–1) and are not perturbed up to pH 10. 2-hole Cu_Z is characterized with absorption and resonance Raman spectroscopies as having two Cu–S stretching vibrations that profile differently. DFT models of the 1-hole and 2-hole Cu_Z sites are correlated to these spectroscopic features to determine that 2-hole Cu_Z has a μ₂-sulfide edge ligand at neutral pH. The slow two electron (+1 proton) reduction of N₂O by 1-hole Cu_Z is discussed and the possibility of a reaction between 2-hole Cu_Z and O₂ is considered.     

Synthesis of a novel polycyclic ring scaffold with antimitotic properties via a selective domino Heck–Suzuki reaction

The synthesis of a previously undescribed sp³-rich 6-5-5-6 tetracyclic ring scaffold using a palladium catalysed domino Heck–Suzuki reaction is reported. This reaction is high-yielding, selective for the domino process over the direct Suzuki reaction and tolerant towards a variety of boronic acids. The novel scaffold can also be accessed via domino Heck–Stille and radical cyclisations. Compounds based around this scaffold were found to be effective antimitotic agents in a human cancer cell line. Detailed phenotypic profiling showed that the compounds affected the congression of chromosomes to give mitotic arrest and apoptotic cell death. Thus, a novel structural class of antimitotic agents that does not disrupt the tubulin network has been identified.     

Impact of Pore Size and Defects on the Selective Adsorption of Acetylene in Alkyne-Functionalized Nickel(II)-Pyrazolate-Based MOFs

C₂H₂/CO₂ separation is a highly challenging process as a consequence of their similar physicochemical properties. In this work we have explored, by static and dynamic gas sorption techniques and computational modelling, the suitability of a series of two isoreticular robust Ni(II)pyrazolate-based MOFs, bearing alkyne moieties on the ligand backbones, for C₂H₂/CO₂ separation. The results are consistent with high adsorption capacity and selectivity of the essayed systems towards C₂H₂ molecules. Furthermore, a post-synthetic treatment with KOH ethanolic solution gives rise to linker vacancy defects and incorporation of extraframework potassium ions. Creation of defects is responsible for increased adsorption capacity for both gases, however, strong interactions of the cluster basic sites and extraframework potassium cations with CO₂ molecules are responsible for a lowering of C₂H₂ over CO₂ selectivity.     

Superior diagnostic strength of combined contrast enhanced MR-angiography and MR-imaging compared to intra-arterial DSA in liver transplantation candidates.

To evaluate the diagnostic value of combined contrast enhanced MRA (ce-MRA) and MRI compared to that of intra-arterial DSA (i.a.DSA) in liver transplantation, transjugular porto-systemic (TIPSS) and spleno-renal shunt candidates. 50 patients in the workup for liver transplantation underwent ce-MRA/MRI and i.a.DSA within a three days interval. Both examinations were assessed with respect to vessel anatomy and patency of the arterial, portal venous, porto-systemic collateral and systemic venous system. The results were compared with the intra-operative findings when available. Malignancy detection in ce-MRA/MRI and i.a.DSA were compared. There are no significant differences for the arterial part of the vascular supply to the liver that is important for transplantation. Although the differences for the portal system are not significant, the difference between the two techniques is of clinical importance because i.a.DSA failed to detect portal vein occlusion in 4 patients. Ce-MRA is significantly better for the detection of collaterals (p < 0.001) and the assessment of the inferior vena cava, the hepatic and the renal veins (p < 0.001). Although the detection of liver malignancy is poor in both techniques, ce-MRA/MRI is superior to i.a.DSA. This study shows that a one step diagnostic approach with a combination of ce-MRA and MRI is a valuable radiological tool with a superior diagnostic strength compared to i.a.DSA in the liver transplantation and shunt candidate. Therefore, ce-MRA/MRI should replace i.a.DSA in these patients groups.     

Electrochemical characterization of plasticized polymer electrolytes based on ABS/PMMA blends

Electrochemical characteristics of plasticized polymer electrolytes based on poly(acrylonitrile-butadene-styrene) and poly(methyl methacrylate) (abbreviated as ABS/PMMA) blends have been studied. The ionic conductivity of the polymer electrolyte with an ABS/PMMA ratio of 6/4 and a plasticizer content of 60% was highest when the LiClO₄ content was 4.8%. The transference numbers (T ₊) of the polymer electrolytes were measured using the steady-state current method, and the T ₊ values were found to be less than 0.5. The electrolyte system was found to have an electrochemical stability window up to 4.5 V. The properties of the electrode interface in contact with the polymer electrolyte were also investigated by impedance spectroscopy, and the evolution of these spectra as a function of storage time was explained and interpreted using a solid-polymer layer (SPL) model. The time evolution of the impedance parameters indicated that a passivation film grew rapidly on the lithium surface immediately after assembly of the cell. Electronic Publication     

Capillary electrochromatography with macroporous particles.

The performance of macro-porous particles in capillary electrochromatography is studied. Three reversed-phase stationary phases with pore diameters between 500 A and 4000 A have been tested for separation efficiency and mobile phase velocity. With these stationary phases, a large portion of the total flow appears to be through the pores of particles, thereby increasing the separation efficiency through a further decrease of the flow inhomogeneity and through enhancement of the mass transfer kinetics. The effects of pore size and mobile phase composition on the plate height and mobile phase velocity have been studied. With increasing buffer concentrations and larger pore diameters, higher mobile phase velocities and higher separation efficiencies have been obtained. Columns packed with 7 microns particles containing pores with a diameter of 4000 A generated up to 430,000 theoretical plates/m for retained compounds. Reduced plate heights as low as 0.34 have been observed, clearly demonstrating that a significant portion of the flow is through the pores. For the particles containing 4000 A pores no minimum was observed in the H-u plot up to linear velocities of 3.3 mm/s, suggesting that the separation efficiency is dominated by axial diffusion. On relatively long (72 cm) columns, efficiencies of up to 230,000 theoretical plates/column have been obtained under non-optimal running conditions. On short (8.3 cm) columns fast separations could be performed with approximately 15,000 theoretical plates generated in less than 30 s.     

(2+4)-Cycloaddition with Singlet Oxygen. 17O-lnvestigation of the Reactivity of Furfuryl Alcohol Endoperoxide¶

In earlier work, the use of furfuryl alcohol as a specific singlet oxygen acceptor was proposed because of the high ratio between the rate constants of chemical reaction and physical quenching. In contrast to furfuryl aldehyde, a number of products are formed by this type II photo-oxidation of furfuryl alcohol. These products may be derived from the endoperoxide of furfuryl alcohol as a common intermediate. The present work focuses on the reactivity of this endoperoxide that was marked specifically by the use of ¹⁷O₂ as a source for singlet oxygen. The analyses of the stable products, their yields and their labeling distribution reveal a strong solvent effect on the primary reaction pathways, and nucleophilic substitution reactions leading to hydroperoxide intermediates are dominant.