Reproducibility in capillary supercritical fluid chromatography: Comparison of injection techniques

An analysis of the precision obtained using commercially available microvalve injectors is reported for three modes of injection: conventional split; timed-split; and direct. Results from this study show that good precision (< 3% RSD for external standard and < 1% RSD for internal standard methods) can be obtained with capillary supercritical fluid chromatography (SFC). However, particular attention must be paid to the type of valve used, the orientation of the column relative to the valve, the mode of interfacing or connecting the column to the valve, and the type of pressure or density programming used for the analysis as all of these factors will affect the reproducibility.     

Pore anisotropy and microporosity in nanostructured mesoporous solids

In this study, we carried out an investigation related to the determination of the anisotropy (b) of pores as well as the extent of microporosity (mic%) in various groups of nanostructured mesoporous materials. The mesoporous materials examined were fifteen samples belonging to the following groups of solids: MCM-48s, SBA-15s, SBA-16s, and mesoporous TiO(2) anatases. The porosities of those materials were modified either during preparation or afterward by the addition of Cu(II) species and/or 3(5)-(2-pyridinyl) pyrazole (PyPzH) into the pores. The modification of porosity in each group took place to make possible the internal comparison of the b and mic% values within each group. The estimation of both the b and mic% parameters took place from the corresponding nitrogen adsorption-desorption isotherms. The new proposed method is able to detect a percentage of microporosity as low as a few percent, which is impossible by any of the methods used currently, without the use of any reference sample or standard isotherms. A meaningful inverse relationship is apparent between the b and mic% values, indicating that large values of b correspond to small values of mic%.     

Quantification of dispersed phase concentration using light sheet imaging methods

With the prevalence of particle image velocimetry (PIV) as a quantitative tool for fluid mechanics diagnostics, its application for analyzing complicated multiphase flows has been steadily increasing over the last several decades. While the primary issue in using PIV for multiphase flows is in separating the information of the phases for independent analysis with a minimum of spurious “cross-talk,” an equally crucial but often overlooked point is in the accurate quantitative measurement of the dispersed phase concentration. Accurate concentration measurement is important due to the fact that the dispersed phase is often heterogeneously distributed in both space and time, either due to a non-uniformity of the source of particulates (such as a spray nozzle or sediment boundary) or due to inertial migration of the particles even from originally homogeneous spatial distributions. In the current work, we examine the effects of light sheet profile distortion and attenuation by tracer seeding particles, as well as reflected light from local wall boundaries on the effective light sheet thickness. The effective thickness is critical for concentration measurements, as it dictates the dispersed phase detection volume. A direct calibration method is demonstrated to measure the effective light sheet thickness in a water/glass bead system, which shows that systematic bias errors on the order of 30% can result if the reflective bed condition is not accounted for, and the errors can be as high as 50% or more if a single-point measure of the sheet width is used.     

Heteroleptic FeII Complexes of 2,2′‐Biimidazole and Its Alkylated Derivatives: Spin‐Crossover and Photomagnetic Behavior

Three iron(II) complexes, [Fe(TPMA)(BIM)](ClO₄)₂?0.5H₂O ( 1 ), [Fe(TPMA)(XBIM)](ClO₄)₂ ( 2 ), and [Fe(TPMA)(XBBIM)](ClO₄)₂ ?0.75CH₃OH ( 3 ), were prepared by reactions of Fe^II perchlorate and the corresponding ligands (TPMA=tris(2‐pyridylmethyl)amine, BIM=2,2′‐biimidazole, XBIM=1,1′‐(α,α′‐o‐xylyl)‐2,2′‐biimidazole, XBBIM=1,1′‐(α,α′‐o‐xylyl)‐2,2′‐bibenzimidazole). The compounds were investigated by a combination of X‐ray crystallography, magnetic and photomagnetic measurements, and Mössbauer and optical absorption spectroscopy. Complex 1 exhibits a gradual spin crossover (SCO) with T_1/2=190 K, whereas 2 exhibits an abrupt SCO with approximately 7 K thermal hysteresis (T_1/2=196 K on cooling and 203 K on heating). Complex 3 is in the high‐spin state in the 2–300 K range. The difference in the magnetic behavior was traced to differences between the inter‐ and intramolecular interactions in 1 and 2 . The crystal packing of 2 features a hierarchy of intermolecular interactions that result in increased cooperativity and abruptness of the spin transition. In 3 , steric repulsion between H atoms of one of the pyridyl substituents of TPMA and one of the benzene rings of XBBIM results in a strong distortion of the Fe^II coordination environment, which stabilizes the high‐spin state of the complex. Both 1 and 2 exhibit a photoinduced low‐spin to high‐spin transition (LIESST effect) at 5 K. The difference in the character of intermolecular interactions of 1 and 2 also manifests in the kinetics of the decay of the photoinduced high‐spin state. For 1 , the decay rate constant follows the single‐exponential law, whereas for 2 it is a stretched exponential, reflecting the hierarchical nature of intermolecular contacts. The structural parameters of the photoinduced high‐spin state at 50 K are similar to those determined for the high‐spin state at 295 K. This study shows that N‐alkylation of BIM has a negligible effect on the ligand field strength. Therefore, the combination of TPMA and BIM offers a promising ligand platform for the design of functionalized SCO complexes.     

Application of the quasi-variational coupled cluster method to the nonlinear optical properties of model hydrogen systems

We present a pilot application of the recently proposed quasi-variational coupled cluster method to the energies, polarizabilities, and second hyperpolarizabilities of model hydrogen chains. Relative to other single-reference methods of equivalent computational complexity, we demonstrate this method to be highly robust and especially useful when traditional coupled cluster theory fails to perform adequately. In particular, our results indicate it to be a suitable method for the black-box treatment of multiradicals, making it of widespread general interest and applicability.     

Identification of a major new involatile N-nitroso compound in smoked bacon

The new N-nitroso compound identified in smoked bacon is 2-(hydroxymethyl)-3-nitrosothiazolidine-4-carboxylic acid. Identification was based on comparison of data from liquid chromatography, capillary gas chromatography and mass spectrometry with those for the authentic compound, the synthesis of which is described.     

Nachweis, Bestimmung und Trennung des Zirkoniums von anderen Elementen

Ohne Zusammenfassung     

Identification of novel bladder tumour suppressor genes

Many genetic alterations have recently been identified in transitional cell carcinoma (TCC) of the bladder. These include alterations to known proto-oncogenes and tumour suppressor genes and the identification of multiple sites of nonrandom chromosomal deletion which are predicted to define the location of as yet unidentified tumour suppressor genes. This review summarises recent efforts to define the location of novel bladder tumour suppressor genes using loss of heterozygositiy (LOH) and homozygous deletion analyses and to isolate the genes targeted by these deletions. For three of the four regions of deletion on chromosome 9, the most frequently deleted chromosome in TCC, candidate genes have been identified. It is anticipated that the identification of the genes and/or genetic regions which are frequently altered in TCC will provide useful tools for diagnosis, prediction of prognosis, patient monitoring and novel therapies.     

Studies on constituents of Abies grandis: The structures and absolute stereochemistry of cyclograndisolide and epicyclograndisolide,novel cyclopropane triterpene lactones

The light petroleum extract of grand fir [Abies grandis (Dougl.) Lindl.] was found to contain two novel triterpene lactones. The first compound, named cyclograndisolide, was shown by chemical and spectroscopic considerations and finally confirmed by X-ray analysis to be (23 R)-3α-methoxy-9,19-cyclo-9β-lanost-24-ene-26,23-olide (6). The second component, epicyclograndisolide was isomeric with the first and was assigned as (23 S)-3α-methoxy-9,19-cyclo-9β-lanost-24-ene-26,23-olide (10).