Table of contents

The sophisticated manual techniques developed to access genetic information encoded in the human genome have yielded a disappointingly small fraction of the knowledge potentially available and automatic methods are now being developed by instrument engineers in an attempt to accelerate the process of biotechnology data capture. The author describes the structure of deoxyribonucleic acid (DNA) and its function as a genetic database. Methods of charting the human genome are outlined and a more detailed account of the Sanger DNA sequencing method is provided. The automation of aspects of material manipulation and separation science relevant to recombinant DNA technology are described. A variety of novel techniques to image labelled DNA fragments separated on electrophoresis gels are detailed together with an outline of automatic methods under development to abstract and process genetic information from the gel band patterns.

Describes a method of comparing large masses using commercial load cells. The results were recorded and analyzed using a microcomputer. The tests described show that deadweight machine masses of 2 tonnes can be compared with an uncertainty of 1 PPM using equipment generally available in a force standards laboratory. Further tests using an overhead gantry crane show that large masses can be compared with an uncertainty better than 5 PPM under less ideal conditions. The results indicate that the method would be useful for the verification of large masses and provide an alternative to the use of either equal arm balances, or mass comparators based on the use of load cells under constant load.

An analysis is made of the noise reduction and peak distortion arising from various methods of digital smoothing. The use of a range of convolutional smoothing algorithms and their multiple repeats, N is first considered. It is found that the width of the peak and the noise reductions arising from multiple repeats follow the expected N^0.5 and N^0.25 dependencies, respectively, only for convolution functions that have all their factors positive. The introduction of negative contributions weakens the dependence on N and introduces oscillations in the background until, at equal strengths of the positive and negative contributions, only severe oscillations remain. Multiple repeats of those functions with only positive factors closely approach a Gaussian function. It is shown that, of the convolutional smoothing algorithms, the traditional Savitzky-Golay methods give the best smoothing for the least distortion of a natural peak shape. These methods are as effective as the optimal Wiener filter and, in turn, may be applied by an optimal rule.

The authors have developed a new geometry for a transient heat pulse technique to measure simultaneously the specific heats and thermal diffusivities of solids. This method is generally applicable to both bulk samples and freestanding thick films of low diffusivity materials. The advantages of the method include easy sample preparation, relatively simple data analysis and high sensitivity.

Two coincidence techniques for simultaneously obtaining particle size and temperature in a plasma torch are described. The absolute magnitude of scattered laser light is used to determine particle size while particle temperature is determined using a two-colour pyrometer technique. Typical results on alumina particles injected into a 7 kW plasma torch are presented.

A kicker magnet accumulates an electron beam in a compact synchrotron radiation ring. The pulsed magnetic field distribution produced by the magnet was measured by the fibre-optic magnetic-field sensor for a bandwidth of 1 MHz. The results of the measurements were satisfactory. The authors measured a uniform field within a radial distance of 80 mm. They began to construct the ring in April 1985 and completed it at the end of that year.

An apparatus is described for generating and controlling magnetic field gradients. It is used in conjunction with standard high-resolution NMR spectrometers to perform NMR imaging experiments. Profiles for G_x, G_y and G_z gradients are digitally stored in separate memories which are loaded via a simple personal computer and are strobed out under spectrometer control. The system is versatile, low cost, simple to interface and use, and does not interfere with normal spectrometer operation.

The authors develop and use a particle sizer designed to measure relatively large individual particles (50 to 400 mu m) over a large sample volume cross section (3*3 mm²). They document the accuracy of the sizer using monodisperse droplets of water and n-decane. They also examine the effect of combustion on particle sizer performance by comparing the results obtained for burning n-decane droplets with results of non-burning tests.

A high sensitivity laser interferometer for the detection of small amplitude, high bandwidth displacements on metal surfaces is discussed. The design is based on the Michelson interferometer but allows multiple reflections of the probe beam from the sample surface. A prototype interferometer and theoretical modelling indicates that the sensitivity of the Michelson interferometer can be increased five times over the simple instrument, suggesting that displacements close to 1 picometer with a bandwidth of 10 MHz may be detected by optical interferometry.

The design of a simple discharge-heated copper vapour laser (DHCVL) is presented and its output characteristics studied. An auxiliary power supply is used to precondition the discharge tube so as to eliminate the possibility of thyratron damage. The laser gives an average power of 20 W at a repetition rate of 5 kHz. Helium was used as the buffer gas.

The design and operational characteristics of a high repetition rate TEA CO₂ laser are described. The laser operates at variable pulse repetition frequencies up to 100 Hz. Stable operation is obtained in a closed cycle which includes a gas mixture regenerator. Energies of up to 10 J/pulse are obtained in pulses having 25 MW peak powers. Average powers as high as 500 W are reached at the maximum pulse repetition frequency. The performance of optical components at various pulse repetition frequencies is presented.

The authors present results from the processing of data obtained from the reflection of broadbeam ultrasonic pulses from a selection of surfaces. The main aim is to produce height distribution curves of these surfaces. Surfaces tested include specially designed grooved surfaces, a paint layer and a hidden stepped surface. The effects of tilt are also investigated. Two signal processing methods are compared: the maximum entropy method and the Wiener-Hopf filter. It is demonstrated that maximum entropy produces not only more visually pleasing output, but also output that shows very close correspondence with the desired result. Comparison with a conventional stylus instrument is provided, and although resolution capabilities are different, a method of comparison is given. Future aims and problems to be overcome in producing a practical instrument are discussed.

A method has been developed to measure the absolute hypersonic absorption of liquids in the frequency range from 0.3 to 3 GHz with 1% accuracy using a pulse transmission technique. Excitation of surface vibrations on small rod-shaped piezoelectric LiNbO₃ crystals at variable transducer spacing is combined with a direct parallel RF substitution technique in which a below-cut-off piston attenuator is used as reference. Sensitive superheterodyne detection followed by signal averaging and multiple data recording allow for a low input power level so that heating of the small sample volume (<1 ml) is avoided. The measurements are automatically driven by a process control control.

The pulsed ultrasonic cross-correlation system is attractive for measuring the dynamic flow characteristics of two component liquid/gas mixtures because the sensors are invasive but do not extend into the pipe and, in contrast to previous continuous wave systems, have a uniform spatial sensitivity due to the absence of standing waves. The potential for measuring the flow characteristics in industrial processes including oil/gas risers is demonstrated by the measurement of the double peak cross-correlation function caused by the 'saddle' velocity distribution encountered in these risers. A theoretical model for the measurement of bubble velocity is developed and supported by experimental results.

The authors demonstrate the simultaneous measurement of fluorescence decays at different emission wavelengths using single-photon timing array detection.