A Tritium–Hydrogen Exchange Procedure for Determining the Concentration of Exchangeable Sites on PAN Based Carbon Fibres

1997 ◽  
Vol 9 (3) ◽  
pp. 281-290 ◽  
Author(s):  
Ian Hamerton ◽  
John N Hay ◽  
Brendan J Howlin ◽  
John R Jones ◽  
Shui-Yu Lu ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Active Sites ◽  
Hydrogen Exchange ◽  
The Other ◽  
Carbon Fibres ◽  
Other Hand ◽  
Non Destructive

A non-destructive tritium–hydrogen exchange procedure has been developed in order to determine the concentration of exchangeable hydrogens on surfaces, and in this particular instance it has been used on carbon fibres. The results show that the concentrations of ‘active sites’ on the surfaces of Courtaulds Grafil XAS and XAU carbon fibres are 2.61 and 0.08 μmol g−1 respectively. When the XAS fibres are subjected to a standard methylation procedure the concentration of exchangeable hydrogens is reduced to 0.79 μmol g−1.On the other hand, when XAU fibres are subjected to oxidation in concentrated nitric acid, the concentration of exchangeable hydrogens is increased to 10.27 μmol g−1.

scholarly journals The Contribution of Geophysics to the Knowledge of the Hidden Archaeological Heritage of Montenegro

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 187 ◽  
Author(s):  
Marilena Cozzolino ◽  
Mile Baković ◽  
Nikola Borovinić ◽  
Giorgia Galli ◽  
Vincenzo Gentile ◽  
...  
Keyword(s):  
Cultural Heritage ◽  
Geophysical Methods ◽  
The Other ◽  
Buried Structures ◽  
Archaeological Heritage ◽  
Other Hand ◽  
The Rich ◽  
Non Destructive

Montenegro is a land of great history which needs attention and care for a deeper knowledge and its making at the disposal of new generations. It is still a territory to be discovered, studied, and disclosed. It is important to understand how much hidden heritage there is still in this area to explore and exploit, but on the other hand, how much known heritage exists to protect and monitor, preventing its destruction and loss. In this context, Montenegro is heavily investing in the management of cultural heritage through initiatives for identification, protection, preservation, enhancement and fruition of them. In the frame of the knowledge, the use of non-destructive geophysical methods can be helpful for a cognitive investigation immediately in the bud of any archaeological verification project, safeguarded through preventive archaeology operations and the exploration of large areas within archaeological parks. In this paper, the results of geophysical prospections at the Hellenistic-Illyrian site of Mjace, the roman towns of Doclea and Municipium S, the medieval city of Svač, and the Stećci medieval tombstones graveyards of Novakovići, Žugića, and Plužine are presented. The study allowed the reconnaissance of new buried structures in the soil and has provided an updated view of the rich archaeological heritage of Montenegro.

Effects of High Concentrations of KC1 and NaCl on Responses of Malate Dehydrogenase (Decarboxylating) to Malate and Various Inhibitors

1974 ◽  
Vol 1 (1) ◽  
pp. 15 ◽  
Author(s):  
H Greenway ◽  
AP Sims
Keyword(s):  
Malate Dehydrogenase ◽  
Active Sites ◽  
Substrate Inhibition ◽  
Maximum Velocity ◽  
Inhibitory Effect ◽  
The Other ◽  
Appreciable Change ◽  
Other Hand ◽  
The Hill ◽  
Hill Number

The effects of KC1 on catalytic and allosteric properties of malate dehydrogenase (decarboxylating) were studied. Chloride salts (50 mM and higher) strongly inhibited enzyme activity at low malate concentrations. At high malate (4 mM) , on the other hand, the degree of inhibition induced by chloride was very small. The s0.5 value (i.e. the malate concentration required for half maximum velocity) was about 0.4 mM in the absence of KC1 and increased to 0.75 and 1.5 mM at 50 and 100 mM KC1 respectively. High chloride concentrations also removed a small degree of substrate inhibition, which in the absence of KC1 occurred at 8 mM malate. At low malate concentrations (< 0 . 5 mM) 50 mM KC1 increased the Hill number from 1.3 to 1.9. Thus chloride treatment revealed a strong degree of cooperativity for the enzyme. This potential for homotropic effects was much less realized in MES buffer (potassium salt), presumably because affinity of malate for individual active sites was already very high. These effects of KC1 were readily reversible and the enzyme showed no appreciable change in molecular weight in the presence of 200 mM KCl. At malate concentrations between 1 and 12 mM, inhibitions of malate dehydrogenase (decarboxylating) activity induced by oxaloacetate, D-malate, and phosphoglycerate were reduced by KCl. At low malate concentrations, on the other hand, the inhibitory effect induced by oxaloacetate changed to a strong stimulatory effect in the presence of KCl. The inhibitory effect due to oxaloacetate was greatly diminished in malate dehydrogenase (decarboxylating) which was eluted from a DE52 cellulose column, but the inhibitory effect due to KC1 was retained. Elution from DE52 cellulose also reduced the Hill number to 1 and increased the s0.5 value. The above results suggest that KC1 reduced the affinity of both substrate and some allosteric inhibitors of malate dehydrogenase (decarboxylating).

COMPARISON OF THE NITROLYSIS OF 1, 3-DICYCLOHEXYLIMIDAZOLIDINE WITH THAT OF HEXAMETHYLENETETRAMINE

1950 ◽  
Vol 28b (5) ◽  
pp. 213-224 ◽  
Author(s):  
J. L. Boivin ◽  
George F Wright
Keyword(s):  
Nitric Acid ◽  
Ammonium Nitrate ◽  
The Other ◽  
Nitrate Salt ◽  
Other Hand ◽  
Dinitro Derivative ◽  
Basic Amine

The nitrolysis of N,N′-dicyclohexylimidazolidine has been effected with formation of the nitrate salt, the nitroso derivative, and the aceto derivative of N,N′-dicyclohexyl-N-nitro-1,2-diaminoethane. The absence of the dinitro derivative suggests that demethylolation is not related to nitramine formation. When formaldehyde splits off to leave a weakly basic amine, as in hexamethylenetetramine nitrolysis, then subsequent nitration will occur; but it will not take place if the resulting amine is strongly basic. Nitrolysis will depend also on reactivity of nitric acid, which can be decreased by addition of ammonium nitrate. This decrease will prevent esterification of intermediate N-methylolamines but not nitrolysis of hexamethylenetetramine types. However both nitrolysis and esterification are thus prevented with dicyclohexylimidazolidine. On the other hand the two nitrolyses are related by the fact that both are accelerated by electropositive chlorine.

On the cause of the reduction of metals from solutions of their salts by the voltaic circuit

1843 ◽  
Vol 4 ◽  
pp. 447-448
Keyword(s):  
Nitric Acid ◽  
Acid Solution ◽  
Large Scale ◽  
Saline Solution ◽  
The Other ◽  
Negative Pole ◽  
Other Hand ◽  
Metallic Salt ◽  
Electric Polarity

The reduction of a metal from its saline solution by the agency of voltaic electricity, has, the author states, been explained in three different ways. By Hisinger, by Berzelius, and by Faraday it has been ascribed to the liberation of hydrogen in this process: Davy and others considered it as resulting directly from the attraction o the metal to the negative pole: and Daniell conceives that the metal is directly electrolysed by the action of the voltaic circuit. The author found that the ends of copper wires, placed in a solution of sulphate of copper between two platina poles in the circuit, mani­fest electric polarity; so that while one end is dissolving, the other is receiving deposits of copper: he also found that platina was, in like manner, susceptible of polarity, although in a much less degree than copper, when placed in similar circumstances. With a view to determine the influence of nascent hydrogen in the voltaic reduc­tion of metals, he impregnated pieces of coke and of porous char­coal with hydrogen, by placing them, while in contact with a metal, in an acid solution, when they thus constituted the negative pole of the circuit; and he found that the pieces thus charged readily re­duced the metals of solutions into which they were immersed; and thence infers that the hydrogen is the agent in these reductions. From another set of experiments he concludes, that during these decompositions, water is really formed at the negative pole; a circumstance which he conceives is the chief source of the difficulties ex­perienced in electro-metallurgic operations when they are conducted on a large scale, but which may be avoided by a particular mode of arranging the elements of the circuit so as to ensure the uniform diffusion of the salt. The author obtained the immediate reduction of gold, platina, palladium, copper, silver and tin from their solutions by the agency of hydrogen contained in a tube, with a piece of platinized platina in contact with the metallic salt: nitric acid and persalts of iron, on the other hand, yielded their oxygen by the influence of the same agent.

Evaluation of the Structural Health of Mechanical Cables

1993 ◽  
Vol 46 (11S) ◽  
pp. S312-S315 ◽  
Author(s):  
Patricio A. A. Laura
Keyword(s):  
Remote Control ◽  
Biomedical Engineering ◽  
Test Methods ◽  
The Other ◽  
Structural Element ◽  
Engineering Applications ◽  
Structural Health ◽  
Destructive Test ◽  
Other Hand ◽  
Non Destructive

Mechanical cables have long been used for towing, for remote control or for the supplying of communication or other service links between two vehicles. They also constitute the basic structural element in suspended bridges. On the other hand they are used in biomedical engineering applications; to lower men underground as deep as 16,000 ft and they are considered in superconductivity applications. Obviously the problem of evaluating the “structural health” of cables or ropes by means of non-destructive test methods is of the utmost importance. This article is concerned with a survey of the available methods.

REACTIONS OF ORGANOTIN COMPOUNDS: VI. THE REACTIONS OF TIN HYDRIDES WITH PERFLUOROVINYL TIN COMPOUNDS

1966 ◽  
Vol 44 (2) ◽  
pp. 179-189 ◽  
Author(s):  
A. D. Beveridge ◽  
H. C. Clark ◽  
J. T. Kwon
Keyword(s):  
Magnetic Resonance ◽  
Ultraviolet Irradiation ◽  
Proton Magnetic Resonance ◽  
Hydrogen Exchange ◽  
The Other ◽  
Organotin Compounds ◽  
Tin Compounds ◽  
Other Hand ◽  
Vinyl Group ◽  
Magnetic Resonance Spectra

The reactions of methyltin hydrides with methylperfluorovinyltin compounds have been examined under heat or ultraviolet irradiation. In no case is there evidence of addition to the C=C bond. Instead, extensive reduction of the vinyl group occurs to give cis-1,2-difluorovinyltin derivatives as the principal products, with smaller amounts of the trans-1,2-difluorovinyltin isomers, 2,2′-difluorovinyltin compounds, and products containing one or more —C2H2F groups. Trimethyl- or dimethyl-tin fluoride is formed quantitatively from the corresponding hydride. In the reaction of dimethyl bis(perfluorovinyl)tin with dimethyltin dihydride, vinyl-hydrogen exchange occurs at 60° in the dark to give dimethylperfluorovinyltin hydride, while under ultraviolet irradiation partially fluorinated vinyltin compounds are formed. On the other hand, no reaction takes place between dimethyl bis(perfluorovinyl)tin and 2 moles of trimethyltin hydride in the dark at 50°, but under ultraviolet irradiation at 25°, partial vinyl-hydrogen exchange occurs, accompanied by reduction, to yield both trimethyl and dimethyl partially fluorinated vinyltin compounds. The infrared and proton magnetic resonance spectra of the products are discussed.

scholarly journals II. Note on the decomposition of sulphuric acid by pentachloride of phosphorus

1856 ◽  
Vol 7 ◽  
pp. 11-15 ◽  
Keyword(s):  
Nitric Acid ◽  
Sulphuric Acid ◽  
Mechanical Mixture ◽  
The Other ◽  
Acid Sulphate ◽  
Other Hand ◽  
Equivalent Quantity

Chemists have long been aware of the fact that some acids unite with bases in one proportion only, others in two or more proportions. Thus a given quantity of nitric acid forms with what is termed its equivalent of potash, a definite nitrate of potash; if less than this equivalent quantity of potash were added to the nitric acid, the product would be a mechanical mixture of the same nitrate of potash with uncombined nitric acid; if more than the equivalent of potash were added, the excess of alkali would remain uncombined. Sulphuric acid, on the other hand, is capable of forming two compounds with potash, and it depends upon the proportions in which the two substances are brought together whether the neutral or acid sulphate is formed.

scholarly journals XX. On the separation of iron from other metals

1821 ◽  
Vol 111 ◽  
pp. 293-299
Keyword(s):  
Nitric Acid ◽  
Large Scale ◽  
The Other ◽  
Exact Method ◽  
General Application ◽  
Other Hand ◽  
Analytical Research

An easy and exact method of separating iron from the other metals with which it may happen to be mixed, has always been a desideratum in chemistry. Every one con­versant with the analysis of minerals is aware of the difficulty of the problem, which indeed is such that, in experiments conducted on any thing like a large scale, it might hitherto be regarded as insuperable. In consequence of this, and of the importance of the enquiry, there is hardly a chemist of eminence who has not proposed some process for the pur­pose, but (with the exception of that which depends on the insolubility of the persuccinate of the obnoxious metal, which I have not tried, and which is too expensive to be resorted to for any but the nicer purposes of analytical research) they are all of them either inadequate to the end proposed, intole­rably tedious, or limited in their application. That which I have now to propose, on the other hand, is liable to none of these objections, being mathematically rigorous, of general application, and possessing in the highest degree the advan­tages of facility, celerity, and cheapness. It is briefly this : The solution containing iron, is to be brought to the maxi­mum of oxidation, which can be communicated to it by boiling with nitric acid. It is then to be just neutralized while in a state of ebullition , by carbonate of ammonia. The whole of the iron to the last atom, is precipitated, and the whole of the other metals present (which I suppose to be manganese, cerium, nickel, and cobalt), remains in solution.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

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