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X-Ray-computed micro-tomography (micro-CT) is relatively well established in additive manufacturing as a method to determine the porosity and geometry of printed parts and, in some cases, the presence of inclusions or contamination. This paper aims to demonstrate that micro-CT can also be used to quantitatively analyse the homogeneity of micro-composite parts, in this case created using laser sintering (LS).

LS specimens were manufactured in polyamide 12 with and without incorporation of a silver phosphate glass additive in different sizes. The specimens were scanned using micro-CT to characterise both their porosity and the homogeneity of dispersion of the additive throughout the volume.

This work showed that it was possible to use micro-CT to determine information related to both porosity and additive dispersion from the same scan. Analysis of the pores revealed the overall porosity of the printed parts, with linear elastic fracture mechanics used to identify any pores likely to lead to premature failure of the parts. Analysis of the additive was found to be possible above a certain size of particle, with the size distribution used to identify any agglomeration of the silver phosphate glass. The particle positions were also used to determine the complete spatial randomness of the additive as a quantitative measure of the dispersion.

This shows that micro-CT is an effective method of identifying both porosity and additive agglomeration within printed parts, meaning it can be used for quality control of micro-composites and to validate the homogeneity of the polymer/additive mixture prior to printing.

This is believed to be the first instance of micro-CT being used to identify and analyse the distribution of an additive within a laser sintered part.

The use of laser sintering (LS) in the medical sector has increased dramatically in recent years. With the move towards direct use of these parts in clinical applications, there is a greater need to understand the effects of standard processes on the part properties. The purpose of this study is to determine the effect that steam sterilisation has on the mechanical properties of LS polyamide 12 parts.

The research presented here focusses on the effect of a single steam sterilisation cycle on the mechanical properties of polyamide 12 parts manufactured using LS. The influence of water content on the properties was investigated, with additional drying steps trialled to establish the potential to reverse any changes observed and to determine their root cause.

The results show that steam sterilisation has a significant effect on the mechanical properties of LS polyamide 12 parts, with a 39% reduction in elastic modulus, a 13% decrease in ultimate tensile strength and a 64% increase in the elongation at break. These properties were also all found to correlate with the water content, suggesting that this was the cause of the difference. The original properties of the parts were able to be recovered after oven drying.

These results show that with an additional drying step, LS polyamide 12 parts can be steam sterilised with no effect on the mechanical properties.

This is believed to be the first investigation into the effects of steam sterilisation in isolation on LS polyamide 12 parts, the first instance of drying parts to recover mechanical properties and the first instance of multiple water content measurements being directly linked to the mechanical properties.

Begins by considering whether the economic theory of the supply, nature and demand for biographies developed by James M. Buchanan and Robert Tollison might apply to this autobiography. Outlines Tisdell’s experiences in his pre‐school years (1939‐1945), at school (1946‐1956) and as a university student (1957‐1963). Covers the period of his first appointment as a temporary lecturer at the Australian National University (1964) and of his postdoctoral travelling scholarship (1965) which took him to Princeton and Stanford and the period of his employment from 1966 onwards. His family and its history are given particular attention.

Vinegar, vin aigre or soured wine is a name that suggests the nature and origin of the substance which is the subject of this note. In France the name is applied to the substance that results from the acetous fermentation of wine. The name has at least the merit of accuracy. The term vinegar has, however, been extended in this country to denote the product obtained by the acetous fermentation of a malt liquor and in the United States of America to mean the substance resulting from the acetous fermentation of cider. In general it may be said that certain kinds of vegetable matter may be made to yield a vinegar by this process. The Census of Production under the common heading “ vinegar and acetic acid ” states that in 1924 the output of these substances, in this country, was 14,200,000 gallons of a value of a little over a million pounds sterling; in 1930 the corresponding figures were 14,600,000 gallons and £950,000; in 1935, 17,100,000 gallons and £790,000. It may be observed that vinegar and acetic acid are not by any means the same thing. Vinegar made by acetous fermentation contains about six per cent. or slightly under that amount of acetic acid as a main and essential constituent, but other substances are present that give it a characteristic bouquet. But whether vinegar be made from malt, wine, cider, or similar substances it is a palatable and wholesome condiment and preservative. It is the result of a biological as distinguished from a chemical process, and we suggest that the term vinegar be limited to the product resulting from the former and not from the latter if it be intended for use in the household as an element in the food supply. The Food Inspectors Handbook, VI Edition, 1913, p. 300, tells us that commercial vinegar is a more or less impure acetic acid. The different varieties according to their source being malt, wine, cider, beet, sugar, and wood vinegars. We cannot think that “ impure acetic acid ” is a particularly happy definition of the term vinegar. It is surely the “ impurities ” the result of secondary reactions that give the characteristic flavour and palatability to vinegar that serve to distinguish it from a merely dilute solution of acetic acid. In the same way whisky might be defined as impure alcohol, but no one, as far as we know; has ever seriously suggested that a dilute solution of absolute alcohol would be a satisfactory substitute for whisky. similarly we suggest that wood vinegar—derived as it is from the distillation of various kinds of wood—is in its origin a purely chemical product and in no sense a biological product. It would follow that if the term vinegar be restricted, as we suggest it ought to be, to the product of biological action the term wood vinegar though well known and often used is really meaningless. The Food Industries' Manual, 1945, written for the guidance of food manufacturers, describes artificial vinegar—made by diluting acetic acid with water and colouring the solution with caramel—as a very poor substitute for the genuine product. “ Artificial vinegar ” it says “is raw in taste and completely lacking in the fine bouquet of characteristic brewed vinegar.” The Extra Pharmacopœia says that vinegar is “also made by diluting acetic acid and colouring with burnt sugar.” The reference however, presumably refers to the use of this kind of “ vinegar ” in pharmacy—vinegar and brown paper for instance—and not as an ingredient in foods.

In the past decade or so, workplace organisation and restructuring processes, have been subjected to the most intense scrutiny. Driven by rapidly intensifying competitive pressures, work organisations sought increased flexibility, especially from labour, as they struggled to maintain market shares in an economic environment increasingly characterised by excess in labour supply. Pressures for change were probably most evident in the public sector where economic and ideological forces combined to limit the growth of government services and increase their exposure to competitive forces.

When men still alive to‐day were young, not a single cargo of chilled or frozen meat, of fruit or of dairy produce from the Southern Hemisphere, had been landed in this country. We have, that is, lived in the last generation through a dietetic revolution which has left us to a large and increasing extent dependent on foodstuffs grown at the ends of the earth and consumed weeks or even months after they leave the places of their origin. Fifty years ago Australia was importing butter, and a century ago the first cow was imported into New Zealand—where there are to‐day more cattle than men. This change in the balance of trade has created a series of new problems in practical science. Some of these have been solved in part, others remain impregnable, and all urgently call for solution; for every year, and almost every month, damage to cargoes is suffered that has its origin in our imperfect knowledge of how to submit perishable goods to the ordeal of prolonged ocean carriage. Beef, to take an obvious example, is hard to bring satisfactorily from Australia. There are two methods by which meat may be preserved, freezing and chilling. The same installation is used in both cases, but for the former, the machine requires to be more powerful, since the temperature of the meat must remain well below 32 degrees F. Mutton lends itself perfectly to freezing, but beef, owing to structural and other causes, is deteriorated if frozen. The tissues are ruptured by expansion, and so, when the meat is defrosted, much of the nutritive liquid escapes. It is possible, that this problem of “drip” may be solved. It is also possible that beef from Australia may be transported to Europe in a chilled (not frozen) state. Experimentally this has already been achieved, but much remains to be done before small scale experiment can be converted into current commercial practice. When it is remembered that there is available in Australia land which would feed a further seven to ten million head of cattle, the importance of the investigations now being conducted into means of transport will be understood. The ocean carriage of fruit involves inquiries equally fascinating and, perhaps, less known. An apple or an orange is not killed by being plucked, but continues to live and “breathe,” that is to say, to absorb oxygen from the air and yield in its place carbon dioxide. In consequence, a ship's hold packed with fruit would quickly resemble a Black Hole of Calcutta were not certain precautions taken. The crowded living cargo threatens to suffocate itself, and the remedy lies in lowering the temperature of the fruit so that it may breathe more slowly, and in the provision of adequate ventilation. Cold, and to a certain extent the expired gas, CO2, itself, lower the rate of living—that is to say, the rate of chemical change, so that the fruit ripens more slowly. It is in this state of delayed ripening that apples from Australia or oranges from South Africa can be brought to this country without damage. Stated in this way, the problem sounds simple enough; given some degree of cold and ventilation, all will be well. As a matter of fact, the limits of temperature and of ventilation within which it is permissible to move are narrowed by both engineering and biological considerations. Living matter does not suffer coercion gladly or passively, and the attempt to delay ripening, though it undoubtedly succeeds, does not leave the fruit at the end where it would be if it had ripened normally. The sequence of chemical change is different; flavouring substances abnormal in character or in amount are apt to be produced, and the problem of successful storage is to hit upon that combination of temperature humidity and ventilation, which will in the end present the product to the palate of the consumer in a state as near to the normal as may be. Fruit, moreover, has its recognisable storage diseases, and, though much advance has been recorded in recent years, losses are still suffered regularly. As an example of the tricks that can be played with plants, it may be mentioned that a rose bush, just budding, can be kept at its “freezing” point and its growth arrested. Then, if it is sheltered under a hothouse roof so that light shines upon it continuously, it will bloom to perfection many months later, when its temperature is allowed to rise. Roses in December arc, in fact, a practical proposition. The stowage of fruit naturally requires particular care. On banana boats, for instance, the chambers are subdivided into pens by portable rails supported in special stanchions, and from the air trunk access may be had to the bananas for inspection during the voyage. To check the danger caused by bulging cases it is sometimes the practice to fit battens around the case ends of thickness equal to the amount of bulge, thus preventing pressure on the fruit itself when the ship rolls. Mere ventilation without refrigeration is sometimes found to be adequate. Provided a good, regular circulation of air is secured, fruit can be brought here and even to America in this manner from the Mediterranean. Ingenious precautions are taken to see that rough weather does not affect storage conditions. In the old days one of the popular methods of artificial lowering of temperature was that of the direct expansion cold air machine. The air from the cargo spaces was sucked into the machine, compressed, cooled, expanded and sent back through the cargo spaces. This system proved, however, unsatisfactory, and has virtually been scrapped. The problem of the elimination of loss from fruit cargoes begins not in the cold store but in the orchard. A layman might expect different varieties of apples to vary in their carrying quantities. But experience has shown that apples of the same kind, even when grown near together and showing no difference if eaten as soon as plucked, vary considerably in their keeping power according to the soil on which they are grown. Thus Victoria plums under standard uniform conditions of commercial storage have had a life varying from one to six weeks. In another case Allington Pippin apples of the 1925 crop, taken from two different trees growing in the same garden less than 15 yards apart, showed a commercial storage life in the same cold store until January, 1926, in one instance, and in the other until May, 1926. Evidently growers, shippers and all concerned in the fruit trade dare not allow such results to be possible, for waste has to be paid for, and if the damage is charged to the public the consumption of fruit is liable to be lowered. It may be feasible to vary keeping quality by modifying soils, and this aspect of the matter, which is, of course, extremely complicated, is being strenuously tackled. If the tasks before scientific investigators are hard, the prizes are valuable. For, apart from the desirability of adding to knowledge, huge commercial interests are at stake. Our capacity for consuming fruit imported from the Southern Hemisphere is only beginning to be tested. It is scarcely too much to say that until after the war we had been accustomed to enjoy apples and oranges only in the colder months. The supplies now on the market all through the summer come wholly from the Southern Hemisphere. South Africa only started exporting oranges in the first decade of the present century, and then only in very small quantities. Now she sends nearly a million cases every season, and it is estimated that this figure could be multiplied tenfold in the next fifteen years if the demand were sufficient. It is such considerations that have led the Empire Marketing Board to give a substantial grant to the Low Temperature Research Institute at Cambridge, which is enabling the Institute to build a new and enlarged station, and considerably to extend its activities in all directions. But producers and consumers are alike dependent on workers in the spheres of low temperature research and soil investigation. These scientific inquirers have much ground to cover before we can claim completely to have learnt the art of carrying perishable cargoes half round the world.—(The New Statesman).

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued