We report a first combination of diamond anvil cell radial x-ray diffraction with in situ laser heating. The laser-heating setup of ALS beamline 12.2.2 was modified to allow one-sided heating of a sample in a diamond anvil cell with an 80 W yttrium lithium fluoride laser while probing the sample with radial x-ray diffraction. The diamond anvil cell is placed with its compressional axis vertical, and perpendicular to the beam. The laser beam is focused onto the sample from the top while the sample is probed with hard x-rays through an x-ray transparent boron-epoxy gasket. The temperature response of preferred orientation of (Fe,Mg)O is probed as a test experiment. Recrystallization was observed above 1500 K, accompanied by a decrease in stress.
: A simple reversible linear motor which steps along a precision track is described. Step size can be varied within the range 0.1 - 5.0 um and final motor position can be adjusted to 0.01 um. More complex versions of the motor and control circuits are also described. The motor uses a piezo-electric tube as the driving element which operates in conjunction with electromagnetic clamps to generate progressive movement. (Author)
A computer-linked microdensitometer has been constructed by fitting a stage with cross-slides driven by impulse motors to a commercial projection microscope. Its accuracy and speed are compared with those of a cathode-ray-tube microdensitometer. The procedure and requirements for analysing x-ray photographs from biological fibres are described.
A simple and easily constructed spectrometer is described by which it is possible to measure the electrical mobilities of submicrometre radioactive aerosol particles with an estimated absolute accuracy to ±4% and a relative accuracy to ±0·5%. The resolution of the instrument is 3% in mobility.
Analyses of the spatial resolution of the Kovasznay vorticity meter and of arrays for measuring velocity derivatives in isotropic turbulence are presented. Pao's three-dimensional spectrum is used, allowing calculations of the measured values of the one-dimensional vorticity spectrum and mean-square velocity derivatives to be compared with their predicted values. It is found that for accurate measurement the array size should be of the order of the Kolmogorov microscale of the turbulence field.
A double-beam recording spectrodensitometer has been constructed to measure the optical density of dry agar electrophoregrammes. The measuring and reference beams are modulated with different frequencies. Two resonance amplifiers separate the signals. The electronic logarithmic recording is independent of the nonlinear characteristics of the valves.
Glass micropipette electrodes with extremely fine tips and high mechanical rigidity have been fabricated with a semi-automatic pipette-puller. The fabrication involves a two stage pull of a heated glass capillary held horizontally by a pair of non-slip clamps. Air is automatically blown from symmetrically located nozzles on to the softened portion of the capillary at the onset of the second pull. With this technique micropipettes with a relatively short taper and large cone angle at the very tip are produced, which not only possess high mechanical rigidity, but also a fineness at the tip (500 Å or less). A special advantage of the large cone angle at the tip is that such an electrode has a much lower electrical impedance than a conventional micropipette electrode with a comparable tip diameter. The size and shape of the micropipette can be easily altered to meet the specific need. The principle of differential vapour pressure has been utilized to fill the micropipettes with the desired electrolytes. A vibration technique for inserting a microelectrode into living cells is also described.
The device described in this note is an automatic means of producing audio signals at random time intervals, and was devised for a work-study project. The system used could be adapted easily for other purposes, for example to the automating of biological experiments requiring random stimuli for behaviour patterns, or to the random sampling of items on a conveyor belt. The system may be used with multichannel outputs and other parameters, e.g. the number of items or events can be used instead of time.
A pump which delivers from 0?01 to 0?65 ml fluid per beat at a frequency of 10-80 beats per min is described. Consecutive discharges agree within 1?5% of the average. Pumping is achieved by rhythmically compressing an elastic tube which has one-way valves at either end. Compression is achieved by oil pressure and controlled by an electronic regulator. This pump surpasses other micropumps with regard to precision, lack of hemolysis and versatility of capacity, frequency and pressure profile.
A mechanical joint has been devised which gives two degrees of freedom to each of three joints in a laser beam steering linkage. This allows accurate counterbalancing of the system and, in conjunction with a CO2 laser, makes the device suitable for use as a surgical tool in `bloodless surgery'.
A conductivity cell incorporating the impingement principle suggested by Nash has been designed to facilitate the continuous measurement of atmospheric sulphur dioxide. The instrument based on this cell is provided with several measuring ranges which can be selected to give full scale deflection from 0·2 to 5 p.p.m. sulphur dioxide.
The construction is described of a simple device by which the fluorescence of very thin liquid layers can be measured. The effect of finite absorbance on the fluorescence yield of the layer is calculated, and compared with experimental values obtained by varying the thickness of a layer containing both fluorescent and absorbing components.
The apparent group movement of spermatozoa in semen is destroyed by shearing but returns as shearing ceases. The time of return is taken as a measure of motility.
The construction of a sensitive spectrophosphofluorimeter is reported. The sensitivity of the detection system has been increased by the use of a cooled selected photomultiplier and a lock-in amplifier or time averaging computer. Essential accessories are the electronic ratio system and the xenon arc stabilization device with a stabilization factor up to 103. Measurements of decay times greater than 0·1 ms for weak signals are possible with this instrument.
A combined oscillator-detector is described for control of laboratory operations by programmed magnetic tape. In addition to eliminating the need to match oscillator and detector frequencies this unit has improved temperature stability, more compact circuitry and built-in controls for sensitivity and sharpness of tuning; this makes it possible to use narrow bandwidths if desired, thus increasing the number of controlling frequencies which can be used in the audio-frequency range of the tape.
Differential scanning calorimetry has been used to investigate the heat of fusion (ΔHf=7·12 kcal per g mol) and true melting temperature (T0=422·4°K) of pure cholesterol (99·5 mole%). In addition to analysis of the thermograph by an existing method a new and more rapid procedure has been used for evaluation of the purity of substances. Evidence is given that differential scanning calorimetry measurements at low scanning rates (0·5,1° min−1), followed by correction for premelting, are essential for estimation of ΔHf of substances not ultra-pure, at higher scanning rates large errors result. The entropy of fusion of cholesterol is similar to that of the simpler cholesteryl esters.
A simple and reliable optical density discriminator is described which possesses a high discrimination sensitivity and low drift.
A simple but versatile aid for the severely disabled is described. It is designed primarily for use by tetraplegics who have no movement below the neck, and works by responding to commands spoken in a form of Morse code. With VOTEM, a patient can control anything normally controllable with switches.
