Calculation of pulsed NMR signal in I = 3/2 quadrupolar spin system

The rf pulse response of I=3/2 spin system experiencing first order quadrupolar splitting is studied using density matrix approach. A general expression is derived in terms of spin populations, quadrupole splitting and duration and amplitude of the rf pulse for calculating the NMR signal arising due to the centre line and satellite resonances for the situation where the impressed rf pulse excites the resonances selectively as well as non-selectively. The necessary 4×4 transformation matrix obtained analytically by diagonalyzing the Hamiltonian are used to get the expression for the centre line response. The satellite signals are obtained in the same way but by using the numerical values of the roots of the related quartics. The widths of the corresponding π/2-pulses are calculated for different initial spin populations. The variations of this pulse-width and the corresponding signal amplitude as a function of satellite splitting are studied.     

Exploiting in situ NMR to monitor the formation of a metal–organic framework

The formation processes of metal–organic frameworks are becoming more widely researched using in situ techniques, although there remains a scarcity of NMR studies in this field. In this work, the synthesis of framework MFM-500(Ni) has been investigated using an in situ NMR strategy that provides information on the time-evolution of the reaction and crystallization process. In our in situ NMR study of MFM-500(Ni) formation, liquid-phase ¹H NMR data recorded as a function of time at fixed temperatures (between 60 and 100 °C) afford qualitative information on the solution-phase processes and quantitative information on the kinetics of crystallization, allowing the activation energies for nucleation (61.4 ± 9.7 kJ mol⁻¹) and growth (72.9 ± 8.6 kJ mol⁻¹) to be determined. Ex situ small-angle X-ray scattering studies (at 80 °C) provide complementary nanoscale information on the rapid self-assembly prior to MOF crystallization and in situ powder X-ray diffraction confirms that the only crystalline phase present during the reaction (at 90 °C) is phase-pure MFM-500(Ni). This work demonstrates that in situ NMR experiments can shed new light on MOF synthesis, opening up the technique to provide better understanding of how MOFs are formed.

A new in situ NMR methodology for studying the formation processes of MOFs is reported, supported by SAXS and PXRD experiments. Synthesis of a phosphonate-based MOF is described, from molecular aggregation through to nucleation and crystallisation.     

Purification of a hybrid plasminogen activator protein

Recombinant DNA technology has been employed to produce a hybrid gene in which the kringle and serine protease domains of tissue plasminogen activator are linked to the heavy-chain Fd region of a fibrin-specific antibody. The hybrid gene is co-expressed with antibody light chains. This communication describes a purification procedure for the hybrid protein, involving affinity and ion-exchange chromatography. The purified hybrid protein has been used in vivo and in vitro clot lysis experiments and has been shown to be effective at clot dissolution.     

Coupled cavity modelocking of a Nd:YAG laser using second-harmonic generation

The modelocking of a Nd:YAG laser using second-harmonic generation in an external cavity as the only pulse shortening process is reported. The output of a long pulse Nd:YAG laser was simultaneously modelocked and Q-switched. The average pulse duration was 30–50 ps and the peak power was in the range 60–160 kW.     

Forecasting practice: organisational issues

Although many surveys have been conducted on forecasting practice, the majority of surveys have investigated the utilisation of forecasting methods and relatively few have studied the role of forecasting in changing organisational structures. The aim of this paper is to address this issue by expanding on earlier case studies which suggested the need for a re-location of the forecasting function within the organisation. Current research has shown how the role of forecasting has changed as organisations adapt to meet the business needs of their customers. The evidence reported in this paper was gathered by surveys and structured interviews carried out in the electronics and financial industries in Scotland.