Medium-Ring Compounds 30. cis-1,6-Cyclodecanediol: Molecular Compounds with the trans Isomer and with Itself

The crystal structures of cis-1,6-cyclodecanediol ( 1 ) and of the molecular compound formed between cis and trans-1,6-cyclodecanediol in the ratio 2:1 (2) have been established by X-ray diffraction. The two substances are closely isostructural. (Crystal data: both monoclinic, P2₁/c, Z = 6; ( 1 ) a = 6.665(6), b = 18.074(3), c = 14.351(8) Å, β = 119.77(6)°, V = 1500(2) ų; (2) a = 6.679(8), b = 18.074(4), c = 14.314(10) Å, β = 119.64(8)°, V = 1502(3) ų). The asymmetric unit of the molecular compound contains one cis molecule in a general position and one trans molecule at a center of symmetry. In the crystal of the pure cis diol a set of disordered cis molecules mimics the corresponding centrosymmetric trans molecules in the molecular compound. The molecules have the stable BCB cyclodecane ring conformation, except for the disordered cis molecules, which have a conformation about 2 kJ mol⁻¹ higher in energy (molecular mechanics calculations). The intricate three-dimensional hydrogen-bond network found in both crystals is presumably especially favorable from an energetic viewpoint.     

Fatigue failure identification by time series model

In this paper an effective way of modeling stochastic strain data, for a fatigue failure identification based on the output response instead of the input is presented. Three steel specimens were tested to fatigue failure under stochastic loading, and autoregressive moving average (ARMA) models of the correlated strain response were determined. The objectives are to be able to identify the dynamics of the failure system, and to describe the current condition of the testpiece by the model parameters, which reflect the physical characteristic of the dynamic process itself for a more realistic assessment of fatigue damage.     

Metabolic disposition of 14C-bromfenac in healthy male volunteers

The metabolic disposition of 14C-bromfenac, an orally active, potent, nonsteroidal, nonnarcotic, analgesic agent was investigated in six healthy male subjects after a single oral 50-mg dose. The absorption of radioactivity was rapid, producing a mean maximum plasma concentration (Cmax) of 4.9 +/- 1.8 microg x equiv/mL, which was reached 1.0 +/- 0.5 hours after administration. Unchanged drug was the major component found in plasma, and no major metabolites were detected in the plasma. Total radioactivity recovered over a 4-day period from four of the six subjects averaged 82.5% and 13.2% of the dose in the urine and feces, respectively. Excretion into urine was rapid; most of the radioactivity was excreted during the first 8 hours. Five radioactive chromatographic peaks, a cyclic amide and four polar metabolites, were detected in 0- to 24-hour urine samples. Similarity of metabolite profiles between humans and cynomolgus monkeys permitted use of this animal model to generate samples after a high dose for structure elucidation. Liquid chromatography/mass spectrometry (LC/MS) analysis of monkey urine samples indicated that the four polar metabolites were two pairs of diastereoisomeric glucuronides whose molecular weight differed by two daltons. Enzyme hydrolysis, cochromatography, and LC/MS experiments resulted in the identification of a hydroxylated cyclic amide as one of the aglycones, which formed a pair of diastereoisomeric glucuronides after conjugation. Data also suggested that a dihydroxycyclic amide formed by the reduction of the ketone group that joins the phenyl rings formed the second pair of diastereoisomeric glucuronides. Further, incubation of various reference standards in control (blank) urine and buffer with and without creatinine indicated that the hydroxy cyclic amide released from enzyme hydrolysis can undergo ex vivo transformations to a condensation product between creatinine and an alpha-keto acid derivative of the hydroxy cyclic amide that is formed by oxidation and ring opening. Further experiments with a dihydroxylated cyclic amide after reduction of the keto function indicated that it too can form a creatinine conjugate.     

The use of hyphenated LC-MS technique for characterisation of impurity profiles during drug development

As part of an integrated quality concept for impurities during drug development, the multidimensional evaluation of impurity profiles by LC MS coupling is presented using peptide drugs as an example. This quality concept can be regarded as an adaptation of the ICH-requirements to the special situation during the drug development process. The primary goal is to obtain qualitative molecular weight information for impurity peaks detected at the same UV wavelength as for the impurity test procedure. The approach is focused on the investigation, if the impurities in a clinical batch were also present in the toxicologically qualified batch(es). Depending on the relevance of individual impurities in further batches or as degradation products, the molecular weight can be used as a starting point for further characterization and identification. Often, eluents with volatile buffers required for MS result in different selectivities and/or inferior chromatographic separation and sensitivity compared with nonvolatile buffers (e.g. phosphates). In these cases, peak 'tracking' especially for small peaks can become critical. A procedure is presented for on-line coupling of LC methods with non-volatile eluents to mass spectrometry.     

Quantitative study of shrinkage and warpage behavior for microcellular and conventional injection molding

This research investigated the effects of processing conditions on the shrinkage and warpage (S&W) behavior of a box‐shaped, polypropylene part using conventional and microcellular injection molding. Two sets of 2^6‐1 fractional factorial design of experiments (DOE) were employed to perform the experiments and proper statistical theory was used to analyze the data. After the injection molding process reached steady state, molded samples were collected and measured using an optical coordinate measuring machine (OCMM), which had been evaluated using a proper R&R (repeatability and reproducibility) measurement study. By analyzing the statistically significant main and two‐factor interaction effects, the results show that the supercritical fluid (SCF) content (nitrogen in this case, in terms of SCF dosage time) and the injection speed affect the S&W of microcellular injection molded parts the most, whereas pack/hold pressure and pack/hold time have the most significant effect on the S&W of conventional injection molded parts. Also, this study quantitatively showed that, within the processing range studied, a reduction in the S&W could be achieved with the microcellular injection molding process. POLYM. ENG. SCI., 45:1408–1418, 2005. © 2005 Society of Plastics Engineers     

Measurement of weak electric currents in copper wire phantoms using MRI: influence of susceptibility enhancement

The use of magnetic resonance imaging (MRI)-based methods for the direct detection of neuronal currents is a topic of intense investigation. Much experimental work has been carried out with the express aim of establishing detection thresholds and sensitivity to flowing currents. However, in most of these experiments, magnetic susceptibility enhancement was ignored. In this work, we present results that show the influence of a susceptibility artefact on the detection threshold and sensitivity. For this purpose, a novel phantom, consisting of a water-filled cylinder with two wires of different materials connected in series, was constructed. Magnitude MR images were acquired from a single slice using a gradient-echo echo planar imaging (EPI) sequence. The data show that the time course of the detected MR signal magnitude correlates very well with the waveform of the input current. The effect of the susceptibility artefacts arising from the two different wires was examined by comparing the magnitudes of the MR signals at different voxel locations. Our results indicate the following: (1) MR signal enhancement arising from the magnetic susceptibility effect influences the detection sensitivity of weak current; (2) the detection threshold and sensitivity are phantom-wire dependent; (3) sub-μ A electric current detection in a phantom is possible on a 1.5-T MR scanner in the presence of susceptibility enhancement.     

Output feedback gains for a linear-discrete stochastic control problem

For the finite-horizon linear-discrete quadratic stochastic control problem, the control is restricted to be a memoryless linear transformation of the measurement. The two-point boundary value problem that specifies the feedback gain matrices is derived, and an algorithm for solving it is given. An example is solved comparing the cost of the suboptimal control to the optimal control.     

Paired MEG data set source localization using recursively applied and projected (RAP) MUSIC

An important class of experiments in functional brain mapping involves collecting pairs of data corresponding to separate "Task" and "Control" conditions. The data are then analyzed to determine what activity occurs during the Task experiment but not in the Control. Here we describe a new method for processing paired magnetoencephalographic (MEG) data sets using our recursively applied and projected multiple signal classification (RAP-MUSIC) algorithm. In this method the signal subspace of the Task data is projected against the orthogonal complement of the Control data signal subspace to obtain a subspace which describes spatial activity unique to the Task. A RAP-MUSIC localization search is then performed on this projected data to localize the sources which are active in the Task but not in the Control data. In addition to dipolar sources, effective blocking of more complex sources, e.g., multiple synchronously activated dipoles or synchronously activated distributed source activity, is possible since these topographies are well-described by the Control data signal subspace. Unlike previously published methods, the proposed method is shown to be effective in situations where the time series associated with Control and Task activity possess significant cross correlation. The method also allows for straightforward determination of the estimated time series of the localized target sources. A multiepoch MEG simulation and a phantom experiment are presented to demonstrate the ability of this method to successfully identify sources and their time series in the Task data.     

Recent developments in high-efficiency Ga0.5In0.5P/GaAs/Ge dual- and triple-junction solar cells: steps to next-generation PV cells

Dual-junction Ga_0.5In_0.5P/GaAs solar cells on Ge substrates have rapidly gone from small, high-efficiency laboratory cells, to large-area, high-efficiency cells manufactured at Spectrolab in high volume. Over 500,000 of these dual-junction (DJ) cells with 27-cm² area have been produced, with average AM0 load point efficiency of 21.4%. The next step in the evolution of this type of multijunction solar cell has been taken, with the development of triple-junction (TJ) Ga_0.5In_0.5P/GaAs/Ge cells. The addition of the germanium third junction, plus several significant improvements in the device structure, have led to a measured efficiency of 27.0% (AM0, 28°C) at Spectrolab on large-area (>30 cm²) TJ cells. The TJ cell is now in production at Spectrolab. Ga_0.5In_0.5P/GaAs/Ge cells are viable not only for non-concentrating space applications, but also for terrestrial and space concentrator systems. Efficiencies up to 32.3% at 47 suns under the terrestrial AM1.5D spectrum have been achieved.