Point/Counterpoint

POINT: AOP Will See Widespread Adoption Adrian Colyer, Rob Harrop, Rod Johnson, and Alexandre Vasseur AOP offers both the short--and long-term return on investment needed to ensure its widespread adoption. COUNTERPOINT: AOP Has Yet to Prove Its Value Danio Beuche and Cédric Beust Where is the proof that nonhierarchical modularization into aspects makes systems development cheaper or better?     

A novel fluorescence lifetime imaging system that optimizes photon efficiency

Fluorescence lifetime imaging (FLIM) is a powerful microscopy technique for providing contrast of biological and other systems by differences in molecular species or their environments. However, the cost of equipment and the complexity of data analysis have limited the application of FLIM. We present a mathematical model and physical implementation for a low cost digital frequency domain FLIM (DFD-FLIM) system, which can provide lifetime resolution with quality comparable to time-correlated single photon counting methods. Our implementation provides data natively in the form of phasors. On the basis of the mathematical model, we present an error analysis that shows the precise parameters for maximizing the quality of lifetime acquisition, as well as data to support this conclusion. The hardware and software of the proposed DFD-FLIM method simplifies the process of data acquisition for FLIM, presents a new interface for data display and interpretation, and optimizes the accuracy of lifetime determination.     

Animating structure plots: Experiments with a PERQ

A PERQ single user computer can be used to animate structure plots, which is of great assistance when interpreting the results from finite element programs. Excellent appreciation may be obtained of a structure oscillating in complicated natural modes. The technique is also useful for studying deformations due to static forces.     

The work of fracture of epoxy resins

The work of fracture has been measured for some epoxy resins at liquid helium temperature, and when possible, at room temperature.     

Integration of microfabricated devices to capillary electrophoresis-electrospray mass spectrometry using a low dead volume connection: application to rapid analyses of proteolytic digests.

This report describes the development of a compact and versatile, micromachined chip device enabling the efficient coupling of capillary electrophoresis to electrospray mass spectrometry (CE-ESMS). On-chip separation provides a convenient means of achieving rapid sample cleanup and resolution of multicomponent samples (typically 2-5 min) prior to mass spectral analysis. A low dead volume connection facilitating the coupling of microfabricated devices to CE-ESMS was evaluated using two different interfaces. The first configuration used disposable nanoelectrospray emitters directly coupled to the chip device via this low dead volume junction, thereby providing rapid separation of complex protein digests. The performance of this interface was compared with that of more traditional configurations using a sheath flow CE-ESMS arrangement where a fused-silica capillary of varying length enabled further temporal resolution of the multicomponent samples. The sensitivity and analytical characteristics of these interfaces were investigated in both negative and positive ion modes using standard peptide mixtures. The separation performance for synthetic peptides using a chip coated with amine reagent ranged from 26,000 to 58,000 theoretical plates for a sheath flow CE-ESMS interface comprising a 15-cm CE column. Replicate injections of a dilution series of peptide standards provided detection limits of 45-400 nM without the use of on-line preconcentration devices. The reproducibility of migration time ranged from 0.9 to 1.5% RSD whereas RSDs of 5-10% were observed on peak areas. The application of these devices for the analysis of protein digests was further evaluated using on-line tandem mass spectrometry.     

A solution to the ‘training’ problem in superconducting magnets

A major factor in the design of large superconducting magnets is the problem of premature quenching, notably the ‘training’ effect, associated with the use of epoxy resin impregnants.This paper draws attention to the existence of a simple but neglected solution to this problem. A review is given of a series of tests carried out in 1968–1971 which showed that such effects were considerably reduced in the case of solenoid and quadrupole coils impregnated with wax or oil, allowing currents at least 85–90% of the critical value to be achieved consistently and reliably. The tests included a full scale prototype quadrupole (9 cm bore, 40 kG maximum field).A discussion of the mechanical and thermal properties of such coils indicates no reason to doubt their long term reliability, and the adoption of this solution for operational magnets is recommended.     

Co-ordinated changes in cAMP, phosphorylated phospholamban, Ca2+ and contraction following beta-adrenergic stimulation of rat heart

Concentration-dependent changes in cyclic AMP (cAMP), site-specific phosphorylation of phospholamban, the intracellular calcium ([Ca2+]i) transient and contraction were measured in isolated rat ventricular myocytes exposed to the beta-adrenoceptor agonist isoprenaline. Cyclic AMP was measured by [125I]-cAMP scintillation proximity assay, phosphorylation of phospholamban at Ser16 and Thr17 was assessed using a pair of site-specific polyclonal antibodies, and [Ca2+]i was monitored with the fluorescent dye fura 2. Cyclic AMP rose to twice basal levels in the presence of 10(-6) M isoprenaline. The maximum increase in phosphorylation at Ser16 and Thr17 of phospholamban was seen at 10(-7) M isoprenaline. At this stage Ser16 phosphorylation was six times higher, and Thr17 phosphorylation was three times higher than that recorded in the absence of isoprenaline. Phosphorylation at Ser16 correlated more closely with changes in the [Ca2+]i transient and contraction than did phosphorylation at Thr17. This is the first study of its kind to measure simultaneous changes in cAMP, the phosphorylation of phospholamban, the [Ca2+]i transient and contraction over a range of concentrations of beta-agonist. The results suggest that phosphorylation of phospholamban at Thr17 is of lesser physiological relevance to the effects of beta-adrenergic stimulation on the heart than phosphorylation at Ser16.     

The rheology of collapsing zeolites amorphized by temperature and pressure

Low-density zeolites collapse to the rigid amorphous state at temperatures that are well below the melting points of crystals of the same composition but of conventional density. Here we show, by using a range of experimental techniques, how the phenomenon of amorphization is time dependent, and how the dynamics of order-disorder transitions in zeolites under temperature and pressure are equivalent. As a result, thermobaric regions of instability can be charted, which are indicative of polyamorphism. Moreover, the boundaries of these zones depend on the rate at which temperature or pressure is ramped. By directly comparing the rheology of collapse with structural relaxation in equivalent melts, we conclude that zeolites amorphize like very strong liquids and, if compression occurs slowly, this is likely to lead to the synthesis of perfect glasses.