Process scale high-performance liquid chromatography Part I: An optimisation procedure to maximise column efficiency

Summary Scale up of analytical High-Performance Liquid Chromatography (HPLC) to the process scale offers promise as a preferred separation method for many high value fine chemicals, both for development purposes and continuous production. It's early adoption is curtailed by the widely held perception that preparative HPLC is a low efficiency high cost technique of limited application. This view has largely beeen generated by the generalised use of large particle size, low quality angular silica supports, and difficulties with packing methodologies. A systematic study of a new silica, in new axially compressed equipment using Plackett-Burman statistics, has demonstrated that very high efficiences, leading to high capacities, can be attained. This work was conducted in the Chemical Technology Unit, University of Manchester Institute of Science and Technology, P.O. Box 88, Manchester, M60 1QD, UK.     

Observation and analysis of fundamental bending mode of T2O

The absorption spectrum of the ν₂ band of T₂O vapor has been observed at 0.04 cm^?1 resolution. A total of 549 transitions has been assigned; 474 of these have been used to evaluate the rotational constants A, B, and C as well as the fourth-order and sixth-order distortion constants and one eighth-order constant for the upper vibrational state.     

High-K quasiparticle structures in 159Er and 160Er

A series of new strongly coupled high-K, multi-quasiparticle structures have been observed in the light erbium transitional nuclei, ¹⁵⁹Er and ¹⁶⁰Er. The interpretation of these bands is discussed within the framework of the cranked shell model. These sequences, when taken together with the existing quasiparticle excitations, form a near complete set of low-lying, multi-quasiparticle structures on which a coherent series of aligned angular momentum, band crossing and blocking arguments can be based. The measured B(M1)/B(E2) ratios are compared with geometrical calculations to test the proposed configuration assignments. Received: 19 November 1997     

Remanent domain structures in magnetic garnet epilayers after planar saturation

Garnet epilayers with a 〈111〉 axis tilted from the film normal have been subjected to a planar saturating field and their remanent domain structures studied with the Faraday effect. For certain directions of applied field, it is possible to produce a mixed polarity state. The creation of the mixed state is discussed in terms of homogeneous nucleation. The possibility of utilising the mixed state for characterising garnet properties is mentioned.     

Detailed investigation of the β-decay of the 9/2+ ground state of 99Nb to levels in 99Mo

The decay of ⁹⁹Nb to ⁹⁹Mo has been investigated. The use of the ion-guide technique for on-line mass separation and of a Ge-array for γ-ray detection have allowed the observation of decay branchings lower than 10^?3. Mediumspin levels, some already known from reaction studies and new ones at high energy, are populated. The β-feeding patterns of the decays of the 9/2⁺ states in ⁹⁹Nb and in its isotones ⁹⁷Y, and ¹⁰¹Tc are qualitatively reproduced by QRPA calculations.     

Synthesis of the insecticidal 1′-acetoxy-mammeins and surangin b

Methods are examined for the synthesis of 4-(1′-acetoxy) alkylcoumarins having hexasubstituted aromatic rings. This has led to synthesis of the three insecticidal coumarins mammea E/BB, mammea E/BA and surangin B.     

Investigating the Red Shift between in vitro and in vivo Urocanic Acid Photoisomerization Action Spectra

Abstract— Trans-urocanic acid (UCA) is found in the upper layer of the skin and UV irradiation induces its photoisomerization to cis -UCA. Cis -UCA mimics some of the immunosuppressive properties of UV exposure. The wavelength dependence for in vitro photoisomerization of trans-UCA (15 μM) over the spectral range 250 nm-340 nm (10 nm intervals) was determined. The action spectrum revealed that maximal cis-UCA production occurred at 280 nm, which is red-shifted by 10-12 nm from its absorption peak at 268 nm and differs markedly from the reported action spectra for cis-UCA production in mouse skin in vivo , which peaks at 300-310 nm. The reasons for the red shift between the in vitro and in vivo action spectra are not clear. There is limited evidence suggesting that the UV absorption maximum of trans- UCA red shifts from 268 nm in vitro to 310 nm on interaction with stratum corneum proteins in vivo. This phenomenon was investigated by applying trans-UCA (2.5 mg/cm²) in an oil emulsion to isolated human stratum corneum. After incubation at 37°C for 1 h, the absorption spectra of stratum corneum with UCA and with oil only were compared using a Xe arc source and a spectrora-diometer. A moderate red shift in trans-UCA absorption from ∼268 nm to 280 nm was observed. In summary, we suggest that the 10-12 nm red shift between the UCA absorption spectrum peak and the action spectrum peak in vitro may be accounted for by the wavelength dependence of quantum yields reported over the 254-313 nm range. The red shift between the in vitro and in vivo photoisomerization action spectra may result from the 10 to 12 nm red shift in the absorption of UCA in association with stratum corneum proteins, combined with increasing quantum yields over the 254-313 nm range.