Antimicrobial properties of terrestrial snail and slug mucus

Snail and slug mucus is a viscous-elastic substance secreted by specific glands with adhesive and lubricants properties that allows them to adhere tenaciously to many different surfaces. It has been used since ancient times for care and human health and it is still very important in traditional and folkloristic medicine. Recently, mucus from snail and slugs and its protein and components have been subjected to some investigations on their antibacterial, antiviral and antifungal activity due to extensive traditional uses and for a future application in medicine. Antimicrobial activities of crude mucus, and its components, against different microorganism have been reported, showing antimicrobial activities that lead their potential employment in several fields as natural additives. The purpose of this Review is to summarize the results of antimicrobial studies of snail and slug mucus and its compounds from the first scientific applications to the isolation of the single components in order to better understand its application and propose an employment in future studies as a natural antimicrobial agent.

An Advanced Shell Theory Based Tire Model

The objective of this paper is to investigate a class of general tire models that provides results suitable for usage in vehicle dynamics. Tire models currently used for vehicle dynamic analyses are overly simplistic (springs, a spring and damper combination or semi-elastic substance) or based on curve fits of experimental data. In contrast, the tire models used by major tire companies are extremely complex with solutions possible only by finite element analysis. Between these two extremes exists the potential for an elasticity based shell theory tire model. Micro-mechanics and composite laminate theories provide an integrated approach to the macroscopic behavior of the tire carcass and the tread support plies. This methodology has the capability of including centrifugal and friction forces. Finite difference methods are applied that produce reliable and accurate solutions of the tire response.

Footnotes to Stravinsky Studies: ‘Le Sacre du printemps‘

Stravinsky said that he dreamed regularly, that his dreams were ‘the ground for innumerable solutions in my composing activity’. But it is just these composerly dreams about which he has been reticent. Instead, he has recalled the ‘time dreams and counting dreams [which] are common with me, and … dreams in which people shout, but inaudibly’. And again, ‘I am forever trying to tell the time and forever looking at my wrist watch, only to find it isn't there’. Then there was the dream of being a hunchback, which presaged an attack of intercostal neuralgia brought on by nicotine poisoning; another about the scent of Debussy's Eau de Cologne; and one more about his passport, ‘very yellow’. There are no musical portents in these dreams; but of the ones that are musical, the most practical was the one that prescribed the instrumentation of the Octet; and the most bizarre, even Freudian, was the pink dream (‘I often dream in colour’), during the time he was composing Threni, about the two warm, gelatinous, testicular eggs supporting ‘an elastic substance stretching exactly between the two notes [of an interval] I had composed.’ The tension of the stretched substance assured him that his interval was the right one.

‘Corn’

In this country and in those with which we are best acquainted, that large part of the human diet which is derived from grain is mainly eaten in the form of bread. Bread, in order to be palatable and digestible, must be leavened; and this means that the dough must be able to retain some of the carbon dioxide gas produced in it by the agency of yeast or some similar substance. Its capacity for doing this depends upon the presence in the grain of a sufficient amount of proteins of such a kind that when mixed with water they form the elastic substance known as gluten. It is largely because wheat—and especially the species of triticum vulgare to which all our bread wheats belong—is superior to all other grains in this respect that wheat has become the main bread grain of a large part of the world.

The Caoutchol Component of Natural Rubber. A Correction

The author recently described a method, developed in Malaya, for separating natural rubber into two main fractions, one containing, among other things, a hydrocarbon which was called caoutchene; the other including an oxygenated substance which constitutes about 2–5 per cent of natural rubber. The latter, which was named caoutchol, was described as a nontacky, freely soluble, highly elastic substance, for which the formula C80H130(OH)2 was suggested. Caoutchene, constituting 87–91 per cent of total rubber, and isolated only in a crude state, was described as tacky, of low tensile strength, and giving solutions of notably low viscosity, and its elongation under tension was stated not to exceed 200 per cent. It was further suggested that the elasticity of rubber was derived essentially from its minor component, caoutchol. The author has now been able to examine again the substance, in collaboration with his colleagues on the staff of the British Rubber Producers' Research Association. Fresh facts have been brought to light, both here and elsewhere, in consequence of which it has been found necessary to amend or withdraw the suggestions originally put forward. Nevertheless it is emphasized that caoutchol is a naturally occurring substance of real interest, quite distinct from artificially oxidized rubbers.

Rational Processing

The processes to which rubber is subjected before vulcanization depend largely for their success on the raw material being rendered plastic. At ordinary temperatures smoked sheet is an elastic substance having nerve and incapable of being kneaded, extruded or moulded. To facilitate these processes and compounding with fillers, rubber is masticated, either on a two-roll mill or in an internal mixer. Experience has shown that mechanical working reduces the elasticity and nerve of rubber and renders it plastic. Mastication is such a familiar practice in rubber technology that it is taken for granted as the first essential in rubber manufacture. This is unfortunate, because it is costly and has several disadvantages. These will be considered in detail and other means of achieving the same end suggested.

Micromanipulations of Latex in the Dark Field

It can be conclusively proved that the individual particle in latex of Hevea brasiliensis after the evaporation of the dispersing agent is surrounded by an adsorbed layer, probably of protein and resin. In the dispersed condition, the particle shows a difficulty penetrable and not deformable surface. After puncture a highly viscous mass flows out from the interior, and at the moment it comes in contact with the dispersing agent it stiffens to a plastic jelly, while the remaining shell exhibits remarkably elastic properties. After the evaporation of the dispersing agent, there occurs a progressive gelation and transformation into an elastic substance. The same result is obtained when the rubber phase is coagulated by acids or electrolytes. The establishment of this fact is important in connection with the usual preparation of raw rubber. It was proved that the consistency of the particles and the thickness of the elastic shell are dependent on the age of the trees. We are dealing not with a definite membrane, but with a variable enveloping shell whose strength seems dependent on the degree of polymerization of the hydrocarbon. In general the results of the present work prove the latest concepts of the structure of rubber, i. e., the existence of various degrees of polymerization, which can be traced back to the structure of the latex particles.

XXIII.—On the Stresses due to Compound Strains

§ 1. The general problem in elasticity, as usually presented for solution, supposes the elastic substance to pass initially from a state without strain. But important cases exist where it must be conceived to start from a state already under considerable stress. When this is the case, the constitution of the solid undergoes great change, as is shown by the fact that strained glass loses its isotropic property, and becomes doubly refractive. This subject was long ago attacked by Cauchy, who, by means of the theory of molecular actions, deduced the existence, in the expressions for the stresses due to the secondary strains, of terms proportional to the initial or primary stresses. The problem has been since discussed by MM. De St Venant and Boussinesq, who have applied to it Green's expression for the energy stored up during the strain. But the question, in their hands, still retains traces of Cauchy's hypothetical element, inasmuch as their expression for the potential energy was deduced by means of the molecular theory. M. De St Venant even considers it a strong argument for the truth of the latter, that it is indispensable in the discussion of this problem. These authors have also failed to see in what way the remaining part of the potential depends on the original strain.

On the geometrical representation of the expansive action of heat, and the theory of thermo-dynamic engines

The author remarks, that if abscissæ be measured from an origin of rectangular coordinates, representing the volumes assumed by an elastic substance, and if ordinates, at right angles to those abscissæ, be taken to denote the corresponding expansive pressures exerted by the substance, then any succession of changes of pressure and volume may be represented geometrically by the coordinates of a curve. It such a curve have two extremities, the area included between the curve and the ordinates let fall from its extremities will represent (when positive) the expansive power given out by the substance during the process represented by the curve.

Observations on the human urethra, showing its internal structure, as it appeared in the microscope of F. Bauer, Esq

Mr. Bauer has discovered, by the aid of the microscope, that the human urethra is made up of two parts, an internal membrane and an external muscular covering; the former, very thin and destitute of fibres, is thrown into folds in a collapsed state, and upon its surface are numerous orifices of glands; the latter is made up of short interwoven fibres, forming fasciculi united by an elastic substance of the consistence of mucus: these observations show the fallacy of the common opinion, that the lining of the urethra consists of circular contractile fibres, and throw a new light upon the disease called Stricture; a spasmodic stricture being a contraction of a small portion of the longitudinal muscular fibres, while the others are relaxed; and a permanent stricture consisting in the exudation of coagulable lymph, in consequence of inflammation, between the fasciculi of muscular fibres and upon the internal membrane. After adverting to what is known respecting the structure of the corpus spongiosum, and corpora cavernosa, the author proceeds to state the result of Mr. Bauer’s examination of those parts. The cellular structure of the corpora cavernosa is made up of many thin membranous plates, very elastic, and so connected as to form a trellis-work, the edge of which is attached to the elastic ligamentous substance which surrounds them, and which forms the septum that separates them. The structure of the corpus spongiosum resembles that of the corpora cavernosa, except that the parts are formed upon a smaller scale, and that there are no muscular fibres in its ligamentous elastic covering. The various details and descriptions in this paper are illustrated by Mr. Bauer’s drawings.