The measurement of the fluorescence detected circular dichroism (FDCD) from a chiral Eu(III) system

The first measurement of the fluorescence detected circular dichroism (FDCD) from a chiral Eu(III) system, made possible by use of a variable liquid crystal circular polarizer, is reported.     

Multinuclear NMR studies on the sol-gel preparation of sodium aluminophosphate glasses

Sodium aluminophosphate gels and glasses in the system NaPO₃–Al₂O₃ with P/Al ratios ranging from 9:1 to 1:1 have been synthesized by a novel sol–gel route based on the reaction of aluminum lactate with sodium polyphosphate in aqueous solution. The route from the solution to the gel and the final glass was monitored in situ by liquid and solid state NMR techniques, characterizing the influence of composition and pH on the hydrolysis, polymerization, and vitrification processes. The site distribution in the xerogels is strongly influenced by the gel-processing temperature. At temperatures near 150°C ligation with lactate groups can be nearly suppressed, resulting in maximum Al/P connectivity in the gel. Annealing the gels at temperatures near 400°C produces significant structural rearrangements, resulting in a glassy network that has close structural similarity to the glasses derived from the usual melt-cooling procedure at 1100–1450°C. This has been confirmed by extensive ²⁷Al, ³¹P and ²³Na MAS NMR as well as ²⁷Al{³¹P} and ²⁷Al {¹H} double resonance experiments. Compared to melt-cooling, the sol–gel process permits a significant extension of the glass-forming region towards higher alumina contents.     

Studies of cisplatin and hemoglobin interactions using nanospray mass spectrometry and liquid chromatography with inductively-coupled plasma mass spectrometry

Interactions of cisplatin with hemoglobin (Hb) were studied using both nanoelectrospray mass spectrometry (nanoESI-MS) and a combination of size exclusion high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICPMS). Size exclusion HPLC separation of free and protein-bound cisplatin followed by simultaneous monitoring of 195Pt and 57Fe demonstrated the presence of Hb-bound Pt complexes. Nanospray quadrupole time-of-flight mass spectrometry studies of the Hb-cisplatin complexes further demonstrated the specific binding of cisplatin to the alpha-chain, heme-alpha, beta-chain, and heme-beta units of hemoglobin. Accurate mass measurements and tandem mass spectrometry information confirmed the Hb-cisplatin complexes. The formation of Hb-cisplatin complexes was observed at the sub-microM to microM concentration levels of cisplatin, which are relevant to clinical levels. These findings and the techniques developed for cisplatin-Hb interaction studies are useful for understanding of drug-protein interactions.     

Alkane coordination selectivity in hydrocarbon activation by [Tp'Rh(CNneopentyl)]: the role of alkane complexes

The competitive activation of C-H bonds of linear, cyclic, and branched hydrocarbons using the coordinatively unsaturated 16-electron [Tp'RhL] reactive fragment have been studied (Tp' = tris-(3,5-dimethylpyrazolyl)borate; L = CNCH2CMe3). Activation of the hydrocarbons leads to the formation of Tp'Rh(L)(R)(H) alkyl complexes, which were converted to the stable chlorides immediately following the activation of the bonds via photolysis of Tp'Rh(L)(PhN=C=NCH2CMe3) in the solvent mixture. The products were analyzed by 1H NMR spectroscopy. The experiments described provide relative rates for the coordination of primary and secondary C-H bonds to the Rh metal center, indicating a 1.5x preference for the latter.     

Duality of Heights Over Quaternion Algebras

Given a number field K, it is well-known that the height of a subspace in K^N and of its orthogonal complement coincide. We prove the analogous fact when K is replaced by a positive definite rational quaternion algebra with respect to the heights recently introduced by the first author. Since quaternion algebras are non-commutative, we cannot just follow the classical proof but have to work with localizations and certain finite rings.     

The advantage of knowing where to listen

This study examined the role of focused attention along the spatial (azimuthal) dimension in a highly uncertain multitalker listening situation. The task of the listener was to identify key words from a target talker in the presence of two other talkers simultaneously uttering similar sentences. When the listener had no a priori knowledge about target location, or which of the three sentences was the target sentence, performance was relatively poor-near the value expected simply from choosing to focus attention on only one of the three locations. When the target sentence was cued before the trial, but location was uncertain, performance improved significantly relative to the uncued case. When spatial location information was provided before the trial, performance improved significantly for both cued and uncued conditions. If the location of the target was certain, proportion correct identification performance was higher than 0.9 independent of whether the target was cued beforehand. In contrast to studies in which known versus unknown spatial locations were compared for relatively simple stimuli and tasks, the results of the current experiments suggest that the focus of attention along the spatial dimension can play a very significant role in solving the "cocktail party" problem.     

Informational masking for simultaneous nonspeech stimuli: psychometric functions for fixed and randomly mixed maskers

Sensitivity d' and response bias beta were measured as a function of target level for the detection of a 1000-Hz tone in multitone maskers using a one interval, two-alternative forced-choice (1I-2AFC) paradigm. Ten such maskers, each with eight randomly selected components in the region 200-5000 Hz, with 800-1250 Hz excluded to form a protected zone, were presented under two conditions: the fixed condition, in which the same eight-component masker is used throughout an experimental run, and the random condition, in which an eight-component masker is chosen randomly trial-to-trial from the given set of ten such maskers. Differences between the results obtained with these two conditions help characterize the listener's susceptibility to informational masking (IM). The d' results show great intersubject variability, but can be reasonably well fit by simple energy-detector models in which internal noise and filter bandwidth are used as fitting parameters. In contrast, the beta results are not well fit by these models. In addition to presentation of new data and its relation to energy-detector models, this paper provides comments on a variety of issues, problems, and research needs in the IM area.     

Site connectivities in silver borophosphate glasses: new results from 11B{31P} and 31P{11B} rotational echo double resonance NMR spectroscopy

Local and medium range order in the glass system 50Ag2O-50[(B2O3)x-(P2O5)(1-x)] (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) have been investigated by high-resolution solid state nuclear magnetic resonance (NMR) techniques. The detailed local site distribution has been derived from deconvolution analysis of the 11B and 31P magic-angle spinning (MAS) NMR signals. Quantitative information regarding the extent of boron-oxygen-phosphorus connectivity has been obtained on the basis of 11B[31P} and 31P{11B} rotational echo double resonance experiments. Incorporation of borate into silver metaphosphate glasses produces four-coordinate BO4/2- sites, which crosslink the metaphosphate chains, resulting in a significant increase in the glass transition temperature. Furthermore, the presence of borate favors the disproportionation of P(2) chain-like units into P(1) and P(3) sites, an effect not observed in binary alkali phosphate glasses. Finally, borate incorporation beyond x=0.3 results in the formation of neutral BO3/2 units, indicating some net charge transfer from the borate to the phosphate network former species. This latter result corresponds to the general metal ion scavenging effect observed for phosphate species in other mixed network former glass systems. In the present system, the effect is relatively moderate, however, suggesting that anionic BO4/2- groups are stabilized by the interaction with the phosphate groups.     

A simple prediction of total body water to aid quality control in isotope dilution studies in subjects 3-87 years of age

The principal method of measuring total body water (TBW) is by isotope dilution. Also, the doubly labelled water method, which is the method of choice for measuring total energy expenditure (TEE) in free-living individuals, includes calculation of TBW as the dilution space of the tracer. TBW was measured in 261 subjects (135 males and 126 females), aged 3-87, including healthy children, children with HIV and adults with non-insulin dependent diabetes mellitus (type 2 diabetes), mild hypertension, pancreatic cancer and lung cancer, either in studies of body composition or TEE. A linear relationship was found between TBW and height in all subjects. When TBW is plotted against height cubed (Ht3, m3) the regression line can be forced through the origin. Considering only adults with 18.5>body mass index <29.9 and all children (n=220), this yielded TBW (l)=7.40 x Ht3, R2=0.95. This simple linear relationship between measured TBW and Ht3 compared favourably with other prediction methods, assuming TBW is a constant proportion (55%) of body weight and TBW predicted from height and weight (mean difference between measured and predicted TBW 0.55 l compared with -1.95 and -1.20 l, respectively). Absolute errors were greater at higher TBW, but use of a log10 transformation reduced this effect. This simple relationship of TBW with Ht3 is too crude to be used as a body composition predictor in individual subjects as it ignores, for instance, body shape. However, it can be used as a quality control tool. Here, use of a log10 transformation and residual plot can serve to identify outliers, which can be checked for gross errors in data input and if necessary samples are re-analysed.