Experimental Investigation of the Bernoulli Head/Disk Interface

The Bernoulli head/disk interface is investigated using interferometry as well as the measurement of acoustic emission, normal force, and disk deflection. The dependence of head-to-disk spacing on radial head position and velocity for upper and lower heads is measured by monochromatic light interferometry. Acoustic emission measurements are used to study intermittent contacts between head and flexible disk. The normal force between the head and the disk h measured and is found to correlate with the acoustic emission signal. The disk deflection characteristics show that the normal force at the head/disk interface is related to the vertical displacement of the head. The normal force at the head/disk interface is determined from the relative disk deflection using the disk stiffness in the normal direction and compared with the measured force.     

Recognition of chitin and proteins in invertebrate cuticles using analytical pyrolysis/gas chromatography and pyrolysis/gas chromatography/mass spectrometry

Flash pyrolysis/gas chromatography (py/GC) and py/GC/mass spectrometry (MS) have been utilized to characterize the cuticles of invertebrates chemically. Pyrolysis products have been identified and assigned to specific cuticular components. Acetylpyridones, acetamidofuran, 3-acetamido-5-methylfuran and 3-acetamido-(2 and 4)-pyrones are proposed as characteristic pyrolysis markers for chitin. Pyrolysis products displaying ions of m/z 70, 154, 168, 194 are thought to derive from diketopiperazine structures and provide potential markers for proteins and peptides in which proline, alanine, valine, arginine and glycine are the dominant amino acids. These products, constituting specific pyrolysis markers for invertebrate cuticles, may reflect the amino acid composition of their constituent structural proteins. The source of the various pyrolysis products of proteins has been verified by pyrolysis of reference proteins, peptides and amino acid mixtures. The presence of additional pyrolysis products related directly to histidine and catechol moieties is consistent with the chemical structure and composition proposed for arthropod cuticles based on recent work utilizing solid state 13C and 15N nuclear magnetic resonance. This study constitutes the first comprehensive chemical characterization of the pyrolysis products of invertebrate cuticles and provides the basis for future investigations requiring qualitative screening for cross-linked chitin and proteins in modern and fossil cuticles and in materials, e.g. geopolymers, that may be derived from them.     

Design of uncorrelated signals

By considering the identification of a multi-input single-output process, it is shown that it is not possible to design uncorrelated sequences (of the same period) with autocorrelation functions of delta-function form This result is of importance not only in process identification, but also in the field of communication, where much effort has gone into trying to design uncorrelated sequences.     

CONTROLLING MALTING LOSSES WITH ANOXIA,CARBON DIOXIDE,AND SULPHUR DIOXIDE

Micromalting trials were used to evaluate the effectiveness of various treatments with anaeroblosis, carbon dioxide or sulphur dioxide in controlling malting losses with grain treated with gibberellic acid. Periods of increasing anoxia, with carbon dioxide accumulation as in Kropff malting, produced malt with a reduced malting loss and a lower hot water extract than control malting. Covering germinating barley with atmospheres containing various partial pressures of carbon dioxide reduced malting losses, but the resulting malts were usually inferior in quality to the controls. Sulphur dioxide gas, applied to moist germinating barley three days after casting, reduced malting losses by almost 3%, and increased the hot water extract by about 3 lb./Qr. relative to control malts. The treated malt occupied less space than the control, and the heat output was reduced. Sulphur dioxide treatment and only 4 days' germination produced a malt in high yield, with an extract identical to that of a control malt germinated for five days. The sulphur dioxide malts yielded worts with lower pH and higher soluble nitrogen values than the control and the fermentability of the worts was normal.     

Author's reply to comment on: A finite difference scheme for the incompressible advection-diffusion equation

A method of transforming the basic relationships of a flat quadrilateral strain membrane element in the local system into those of a warped quadrilateral strain membrane element in the global system is presented. This procedure removes the finite element modelling restrictions associated with flat quadrilaterals.     

Stability of a two-degree-of-freedom gyro with external feedback

The requirements for insuring the stability of the loop formed when external feedback is applied to a two-degree-of-freedom gyro are determined. The method of analysis also suggests the means for increasing the damping of the nutation of a precessible two-degree-of-freedom gyro when it is used in a free mode.