Gas chromatographic determination of propyphenazone in plasma

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Combined immunological and thin-layer chromatographic method of the determination of morphine

     

Extraction of cross-sections of inelastic scattering from energy spectra of reflected atomic particles

REELS spectra of the electrons reflected off niobium are measured with energy resolution <0.5 eV within the 5–40 eV energy range of the probing beam. The measurements were performed for the scattering angles θ = 45° and θ = 120° by means of two electron guns. The process of energy losses is described within the framework of a model with three different energy loss laws: surface, intermediate, and bulk layers are considered. Differential cross-sections of inelastic scattering are represented in the form of simple equations.     

Influence of multiple elastic scattering on the shape of the elastically scattered electron peak

The influence of multiple elastic scattering on the shape of the energy distribution of elastically scattered electrons is investigated. The energy of the maximum intensity of the detected electrons differs from the probe electron beam energy due to the elastic energy loss. The experimentally observed spectrum is adequately described by a Gaussian distribution with a maximum at the elastic energy loss value. In this paper the peak-broadening mechanisms due to energy-analyzer spread function, probe beam energy distribution and atomic vibration-induced broadening are considered to be independent and of random nature. Analysis of multiple elastic scattering shows some mechanisms leading to the broadening and a shift of the elastic scattering electron energy spectrum from the value defined by single elastic scattering at the certain angle. It is revealed that the magnitude of this shift and the width of energy distribution is determined by ratio (_lin/_ltr)$(l_{\text{in}}/l_{\text{tr}})$, where _lin$l_{\text{in}}$ is inelastic mean free pass, _ltr$l_{\text{tr}}$ is the transport length.     

From h to p efficiently: Implementing finite and spectral/hp element methods to achieve optimal performance for low- and high-order discretisations

The spectral/hp element method can be considered as bridging the gap between the – traditionally low-order – finite element method on one side and spectral methods on the other side. Consequently, a major challenge which arises in implementing the spectral/hp element methods is to design algorithms that perform efficiently for both low- and high-order spectral/hp discretisations, as well as discretisations in the intermediate regime. In this paper, we explain how the judicious use of different implementation strategies can be employed to achieve high efficiency across a wide range of polynomial orders. Furthermore, based upon this efficient implementation, we analyse which spectral/hp discretisation (which specific combination of mesh-size h and polynomial order P) minimises the computational cost to solve an elliptic problem up to a predefined level of accuracy. We investigate this question for a set of both smooth and non-smooth problems.     

A Titanium(IV)‐Based Metal–Organic Framework Featuring Defect‐Rich Ti‐O Sheets as an Oxidative Desulfurization Catalyst

While titanium‐based metal–organic frameworks (MOFs) have been widely studied for their (photo)catalytic potential, only a few Ti^IV MOFs have been reported owing to the high reactivity of the employed titanium precursors. The synthesis of COK‐47 is now presented, the first Ti carboxylate MOF based on sheets of Ti^IVO₆ octahedra, which can be synthesized with a range of different linkers. COK‐47 can be synthesized as an inherently defective nanoparticulate material, rendering it a highly efficient catalyst for the oxidation of thiophenes. Its structure was determined by continuous rotation electron diffraction and studied in depth by X‐ray total scattering, EXAFS, and solid‐state NMR. Furthermore, its photoactivity was investigated by electron paramagnetic resonance and demonstrated by catalytic photodegradation of rhodamine 6G.     

Guidelines for tuning the macropore structure of monolithic columns for high‐performance liquid chromatography

The ability to control the external porosity and to tune the dimensions of the macropore size on multiple length scales provides the possibility of tailoring the monolithic support structure towards separation performance. This paper discusses the properties of conventional polymer–monolithic stationary phases and its limitations regarding the effects of morphology on kinetic performance. Furthermore, guidelines to improve the macropore structure are discussed. The optimal monolithic macropore structure is characterized by high external porosity (while maintaining ultra‐high‐pressure stability), high structure homogeneity, polymer globule clusters in the submicron range, and macropores with a diameter tuned toward speed (small diameter in the 100–500 nm range using short beds) or efficiency (larger macropores in the range of 500 nm–1 μm allowing the use of longer column formats). Finally, promising approaches to control the morphology are discussed.     

Sub‐picosecond Raman spectrometer for time‐resolved studies of structural dynamics in heme proteins

We describe a pump–probe Raman spectrometer based on a femtosecond Ti:sapphire laser, an optical parametric generator and two optical parametric amplifiers for time‐resolved studies, with emphasis on the structural dynamics in heme proteins. The system provides a 100‐fs pump pulse tunable in the range 500–600 nm and a transform‐limited sub‐picosecond probe pulse tunable in the range 390–450 nm. The spectrometer has spectral (25 cm⁻¹) and temporal (∼0.7 ps) resolutions which constitute an effective compromise for identifying transient heme protein species and for following their structural evolution by spontaneous Raman scattering in the time range 0.5 ps to 2 ns. This apparatus was applied to time‐resolved studies of a broad range of heme proteins, monitoring the primary dynamics of photoinduced heme coordination state and structural changes, its interaction with protein side‐chains and diatomic gaseous ligands, as well as heme vibrational cooling. The treatment of transient Raman spectra is described in detail, and the advantages and shortcomings of spontaneous resonance Raman spectroscopy for ultrafast heme proteins studies are discussed. We demonstrate the efficiency of the constructed spectrometer by measuring Raman spectra in the sub‐picosecond and picosecond time ranges for the oxygen‐storage heme protein myoglobin and for the oxygen‐sensor heme protein FixLH in interaction with the diatomic gaseous ligands CO, NO, and O₂. Copyright © 2010 John Wiley & Sons, Ltd.     

Activation of the metal-organic framework MIL-47 for selective adsorption of xylenes and other difunctionalized aromatics

The capacity and selectivity of the metal-organic framework MIL-47 for liquid phase adsorption are shown to heavily depend on the pretreatment of the material, as illustrated in detail by the particular case of selective xylene adsorption. By totally removing the uncoordinated terephthalic acid from the pores and simultaneously avoiding oxidation to nonporous V(2)O(5), pore volume and uptake of xylenes can be maximized. The presence of uncoordinated terephthalic acid in the pores improves the selectivity between p- and m-xylene. Calcination bed thickness and oven geometry influence the optimal calcination procedure. The physicochemical modifications of MIL-47 during its activation are investigated in detail with XRD, SEM, nitrogen physisorption, TGA and diffuse reflectance UV-Vis spectroscopy. Using optimally pretreated MIL-47 as adsorbent for xylene, ethyltoluene, dichlorobenzene, toluidine or cresol isomers, the para-isomer is in each case preferred over the meta-isomer in pulse chromatographic and batch experiments. The role of stacking in the selective adsorption of these isomers is discussed. In the case of the dichlorobenzenes, the meta- and para-isomers can be separated in a breakthrough experiment with a selectivity of 5.0.