Transition metalcarbon bonds XXXVII. platinum acetylide complexes formed from ethynyl alcohols or ethers

Several new platinum(II) acetylide complexes, trans-{Pt[CCCR₁R₂(OR₃)]₂-L₂} (R₁, R₂  H, Me, Et; CR₁R₂  cyclohexylidene; R₃  H, Me or Ph), trans-[Pt(CCCH₂CH₂OH)₂L₂], trans-[Pt(p-tolylacetylide)₂L₂] and trans-[PtX(p-tolylacetylide)L₂] (L  PMe₂Ph or in one case, AsMe₂Ph) have been prepared. Platinum(II) acetylide complexes with tertiary hydroxyl groups are easily dehydrated by acetic anhydride/pyridine to give platinum-enyne complexes. Analogous compounds with primary hydroxyl groups do not dehydrate but give acetates. ¹H and ¹³C NMR data are given and the shift reagent Eu(fod)₃ was used to analyse the ¹H NMR spectrum of trans-[Pt(CCCH₂CH₂OH)₂(PMe₂Ph)₂].     

Reduction of RF-induced sample heating with a scroll coil resonator structure for solid-state NMR probes

Heating due to high power 1H decoupling limits the experimental lifetime of protein samples for solid-state NMR (SSNMR). Sample deterioration can be minimized by lowering the experimental salt concentration, temperature or decoupling fields; however, these approaches may compromise biological relevance and/or spectroscopic resolution and sensitivity. The desire to apply sophisticated multiple pulse experiments to proteins therefore motivates the development of probes that utilize the RF power more efficiently to generate a high ratio of magnetic to electric field in the sample. Here a novel scroll coil resonator structure is presented and compared to a traditional solenoid. The scroll coil is demonstrated to be more tolerant of high sample salt concentrations and cause less RF-induced sample heating. With it, the viable experimental lifetime of a microcrystalline ubiquitin sample has been extended by more than an order of magnitude. The higher B1 homogeneity and permissible decoupling fields enhance polarization transfer efficiency in 15N-13C correlation experiments employed for protein chemical shift assignments and structure determination.     

The effects of sample preparation methods on the variability of the electrospray ionization response for model drug compounds

A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd.     

Gamma-ray spectroscopy with relativistic exotic heavy-ions

Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors (segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed.     

Percolative transport in the vicinity of charge-order ferromagnetic transition in a hole-doped manganite

We report measurements of non-linear charge transport in epitaxial (La_1−x Pr _x )_0.7Ca_0.3MnO₃ thin films fabricated on (100) oriented SrTiO₃ single crystals by pulsed laser deposition. The end members of this series, namely Pr_0.7Ca_0.3MnO₃ and La_0.7Ca_0.3MnO₃ are canonical charge-ordered (CO) and ferromagnetic manganites, respectively. The onset of the CO state in Pr_0.7Ca_0.3MnO₃ is manifested by a pronounced insulating behavior below ∼ 200 K. The CO state remains stable even when a large (∼ 2×10⁵ V/cm) electric field is applied across the thin film samples. However, on substitution of Pr with La, a crossover from the highly resistive CO state to a state of metallic character is observed at relatively low electric fields. The current-voltage characteristics of the samples at low temperatures show hysteretic and history dependent effects. The electric field driven charge transport in the system is modelled on the basis of an inhomogeneous medium consisting of ferromagnetic metallic clusters dispersed in a CO background.     

Quantitative determination of fucoidan using polyion-sensitive membrane electrodes

The use of polyanion and polycation-sensitive membrane electrodes to detect five different preparations of fucoidan is described. Unlike linear polyanionic molecules previously measured with polymer membrane-based electrochemical sensors, fucoidans from marine brown algae are all highly branched, sulfated polysaccharides with varying charge densities and structures, depending on the species of seaweed, method of extraction used and extent of purification. When tridodecylmethylammonium (TDMA) was used as the ion-exchanger, a large, non-equilibrium EMF response was observed over a concentration range of 0.5–50 μg mL⁻¹ fucoidan. Fucoidan was also measured by titration with polycationic protamine, using a dinonylnaphthalene sulfonate (DNNS)-doped membrane electrode as the potentiometric endpoint detector. Potentiometric titration was used to determine the binding ratio between protamine and fucoidan at the neutralization endpoint for each fucoidan preparation. This binding ratio was then used to successfully determine the fucoidan content of commercially available nutritional supplements. Fucoidan was also measured in undiluted blood serum, demonstrating that this method may be applicable for measuring fucoidan for clinical applications.     

The Institute for Operational Research: An Initiative to Extend the Scope of OR

One of the aims in forming the Institute for Operational Research (IOR) in 1963 was to expand the fields of application of OR and to reverse the tendency, then evident, for it to settle down as a mainly in-house, industrial activity deriving its strength from mathematics and the hard sciences, with little research content of its own. The paper outlines the early work done at IOR in pursuit of this mission, especially in multi-organizational settings such as city and regional planning, health services and the building industry. This leads into discussion of the conditions under which the work was done, the style of ‘action-research’ that evolved, its influence at the time, and its relevance to the different circumstances of the present day.     

The Benefits of Using Web-Based Enhancements in an Environmental Chemistry Class

Four semesters of student evaluations of an environmental chemistry class have been analyzed for differences that can be attributed to Web-based enhancements. The enhancements included Web-based lecture notes, reading and problem assignments, bookmark files, and videotaped lectures. We developed these materials as part of a larger project to provide university-level technical courses over the Internet. Student perceptions of the course improved significantly (α = 0.10) after adding Web-based enhancements. Student’s opinion of the instructor improved, but the change is not significant at the 90% confidence level. The student responses to “Was the course challenging?” “Was my interest stimulated?” and “Was the instructor concerned?” were unchanged in the two groups of students. Drop rates were unchanged between the two student groups. The grade-average was nearly identical for the two student groups (82.9% vs. 83.5%), but the grade-distribution changed significantly. The percentage of A’s decreased slightly when Web-based enhancements were added, but the number of B’s increased from 22% to 40%. The percentage of C’s, D’s and F’s decreased for the students with access to Web-based enhancements. These results indicate that Web-based materials helped weaker students improve their performance and, therefore, their opinion of the class and of the instructor was more favorable.