scholarly journals A recording calorimeter for explosions

1907 ◽  
Vol 79 (528) ◽  
pp. 138-154 ◽  
Keyword(s):  
Specific Heat ◽  
Heat Loss ◽  
Practical Importance ◽  
Copper Strip ◽  
Gas Engine ◽  
Coal Gas ◽  
Engine Cylinder ◽  
Solid Explosives ◽  
The Mean

The determination of the rate of loss of heat to the walls of a vessel after an explosion within it is a matter of considerable scientific interest and of practical importance. Hitherto such determinations, if we except the recent work of Dugald Clerk on the loss of heat in the gas engine cylinder, have been based upon a study of the fall of pressure during the cooling of the gases after the explosion. From the pressure the mean temperature can be deduced, and thence, if the specific heat is known, can be found the rate of heat loss at any moment. Such a calculation is, however, obviously unsatisfactory, because the only available values of the specific heat of gases at temperatures above 1500° are based upon explosion experiments, and involve doubtful assumptions as to the amount of loss before combustion is complete. Some means of determining the loss of heat at any instant without any knowledge of specific heat is therefore essential, both for finding the law of cooling of hot gases confined in a closed vessel and for placing on a satisfactory basis the specific heat values obtained from explosion experiments. I have devised a simple means of doing this which appears to be capable of considerable accuracy. It consists essentially in lining the explosion vessel as completely as possible with a continuous piece of copper strip and recording the rise of resistance of the copper strip during the progress of the explosion and the subsequent cooling. Knowing the temperature of the copper and its capacity for heat, the heat that has flowed into it from the gas may be calculated from the resistance, certain corrections being applied for the heat which the copper has lost to the insulating backing. Up to the present I have only used the apparatus for the investigation of the loss of heat after an explosion of coal gas and air, but it might, I think, be applicable, with certain modifications, to finding the heat loss during and after the combustion of solid explosives.

scholarly journals Bakerian Lecture :─On the variation of the specific heat of water, with experiments by a new method

1912 ◽  
Vol 86 (587) ◽  
pp. 254-257 ◽  
Keyword(s):  
Specific Heat ◽  
Experimental Evidence ◽  
Electric Current ◽  
Heat Loss ◽  
Mean Value ◽  
Mechanical Method ◽  
Order Of Accuracy ◽  
Steady Current ◽  
Differential Pair ◽  
The Mean

The question of the variation of the specific heat of water is so fundamental in calorimetry, and the results of different observers and different methods are still so discordant, that no apology is needed for the publication of fresh experimental evidence. The continuous electric method, which I carried out in conjunction with Prof. Barnes, was specially designed to avoid the main sources of error of the older methods in which mercury thermometers and open calorimeters were employed. In this method. the rise of temperature of a steady current of water, heated by a steady electric current in its passage through a fine tube hermetically scaled in a vaccumjacket, was observed with a differential pair of platinum thermometers. Errors due to lag, or to uncertainty of water-equivalent, or to evaporation or heat-loss in transference, were thus eliminated, and a higher order of accuracy was secured in the temperature measurements. The results of the continuous electric method in the case of water showed a variation of specific heat amounting to less than one half of 1 per cent. between 10° and 80°C., with a minimum at 37.6°C., followed by a very slow and steady rise. The mean value from 0° to 100°C. agreed to 1 in 2000 with the experiments of Reynolds and Moorby by the mechanical method, and the values from 5° to 35° C. agreed to a similar order of accuracy with the experiments of Rowland. But the value at 80°C. was 1 per cent. lower than that found by Lüdin's (Zürich, 1895), employing the ordinary method of mixture with an open calorimeter and mercury thermometers. Lüdin's results for the variation over the range 30° to 100°C. agreed more closely with the continuous electric method than those of any previous observers; but showed a minimum at 25°C., and a maximum at 87°C., which could not be reconciled with the experiments of Reynolds and Moorby on the mean specific heat from 0° to 100°C., or with the most probable reduction of Regnault's experiments between 110° and 190°C.

scholarly journals Kinetics of protein–ligand unbinding: Predicting pathways, rates, and rate-limiting steps

2015 ◽  
Vol 112 (5) ◽  
pp. E386-E391 ◽  
Author(s):  
Pratyush Tiwary ◽  
Vittorio Limongelli ◽  
Matteo Salvalaglio ◽  
Michele Parrinello
Keyword(s):  
Drug Design ◽  
Practical Importance ◽  
Binding Pocket ◽  
Water Molecules ◽  
The Mean ◽  
General Protein ◽  
Experimental Values ◽  
Rate Limiting ◽  
Kinetics Of

The ability to predict the mechanisms and the associated rate constants of protein–ligand unbinding is of great practical importance in drug design. In this work we demonstrate how a recently introduced metadynamics-based approach allows exploration of the unbinding pathways, estimation of the rates, and determination of the rate-limiting steps in the paradigmatic case of the trypsin–benzamidine system. Protein, ligand, and solvent are described with full atomic resolution. Using metadynamics, multiple unbinding trajectories that start with the ligand in the crystallographic binding pose and end with the ligand in the fully solvated state are generated. The unbinding rate koff is computed from the mean residence time of the ligand. Using our previously computed binding affinity we also obtain the binding rate kon. Both rates are in agreement with reported experimental values. We uncover the complex pathways of unbinding trajectories and describe the critical rate-limiting steps with unprecedented detail. Our findings illuminate the role played by the coupling between subtle protein backbone fluctuations and the solvation by water molecules that enter the binding pocket and assist in the breaking of the shielded hydrogen bonds. We expect our approach to be useful in calculating rates for general protein–ligand systems and a valid support for drug design.

scholarly journals Determination of the Mean Electrical Axis in Dogs and Cats (Mini-Review)

2018 ◽  
Vol 75 (1) ◽  
pp. 137
Author(s):  
Cristian BROJBĂ
Keyword(s):  
Reference System ◽  
Practical Importance ◽  
Cardiac Diseases ◽  
The Mean

In this study we set out to reveal the practical importance of the determination of the mean electrical axis (MEA) in dogs and cats. The Hexaxial Reference System is used for the determination of the cardiac electrical axis. We described 2 methods, that are used the most frequently and we confirmed that the movement of the mean electrical axis is useful in the diagnosis of cardiac diseases.

scholarly journals Explosions of coal-gas and air

1906 ◽  
Vol 77 (518) ◽  
pp. 387-413 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Calorific Value ◽  
Inert Gases ◽  
Closed Vessel ◽  
Sharp Rise ◽  
Gas Engine ◽  
Coal Gas ◽  
Engine Cylinder ◽  
Cylindrical Form ◽  
Continuous Record

The experiments here described consist in an investigation into the propagation of flame through a mixture of coal-gas and air contained in a closed vessel and ignited at one point by an electric spark. A continuous record is taken of the variation of resistance of fine platinum wires immersed in the gas, at different points; and at the same time and on the same revolving drum the pressure is recorded. The arrival of flame at any wire is marked by a sharp rise in its resistance. Thus the progress of the flame can be traced. Moreover, the rate of rise of temperature of the wire after the flame has reached it is (after certain corrections have been applied) a measure of the velocity with which the gases round about it combine. In this manner it has been possible to settle in the case of certain mixtures, at any rate, the question of “after-burning,” which has long been a matter of controversy in the theory of the gas-engine, and to determine approximately the specific heat of the mixture of CO 2 , H 2 O, and inert gases which are the products of the combustion. Incidentally it has been necessary to find what relation the temperature of a fine platinum wire immersed in the heated gas bears to that of the gas. Burstall, who has measured the temperature in a gas-engine cylinder by means of platinum wires, did not fully investigate this point, and his results are, in consequence, open to doubt. Before proceeding to a detailed account of the apparatus and records obtained it will be convenient to state shortly the principal conclusions reached. The experiments were all made on mixtures of air and Cambridge coal-gas having an average “higher” calorific value of 680 British Thermal Units per cubic foot at 0°C. and 760 mm. The composition of the gas is given in an appendix. The mixture was fired at atmospheric pressure in a vessel of dumpy cylindrical form and of a capacity of 6⋅2 cubic feet, which is shown in section in fig. 1. The combustion was started by an electric spark at the centre of the vessel.

scholarly journals The variation with temperature of the specific heat of sodium in the solid and the liquid state; also a determination of its latent heat of fusion

1914 ◽  
Vol 89 (614) ◽  
pp. 561-574 ◽  
Keyword(s):  
Melting Point ◽  
Specific Heat ◽  
Latent Heat ◽  
Liquid State ◽  
Mean Value ◽  
Heat Of Fusion ◽  
Latent Heat Of Fusion ◽  
The Mean ◽  
Considerable Range

The present paper contains the results of an investigation into the variation, with temperature, of the specific heat of sodium in the solid and the liquid state; also, some determinations of its latent heat of fusion. Our knowledge of the variations of the specific heat of metals in the region of their melting point is extremely vague and hypothetical, since the methods of investigation commonly employed are only capable of giving the mean value of the specific heat over a considerable range of temperature.

scholarly journals II. On the specific heats of minerals

1887 ◽  
Vol 41 (246-250) ◽  
pp. 250-274 ◽  
Keyword(s):  
Specific Gravity ◽  
Specific Heat ◽  
Hollow Structure ◽  
Thermal Constant ◽  
Steam Temperature ◽  
Specific Heats ◽  
Discriminative Value ◽  
The Mean ◽  
In The Beginning

A number of experiments were made on minerals by the method of condensation, using the form of gravimetric calorimeter described in the beginning of the paper on calorimetry (p. 353). The con­densation of steam being in all cases employed, the values recorded are the mean specific heats between atmospheric temperatures ap­proximating to 12° C., and steam temperature, about 100° C. More exactly, the values recorded are the mean calorific capacities for a rise of one degree between the limits t 1 and t 2 , tabulated in each case. The specimens dealt with were chosen as good samples of the mineral free from visible impurities.* But before detailing the particulars of the experiments a few notes on the discriminative value and physical interest attached to this application of calorimetry may not be amiss. It seems probable that the neglect of the use of the specific heat constant is to be ascribed to the difficulties besetting its determina­tion. Certainly if its determination was as easily effected as we effect the determination of the specific gravity of a body, there are on the other hand sufficient reasons to recommend its use as in general of more physical value and interest than the much used specific gravity. There are cases indeed where specific gravity, as it is possible to obtain it, is misleading, and where specific heat gives at once valuable information on the probable chemical nature of the substance. Such eases would arise with bodies of loose vesicular or hollow structure. No misleading variations need be introduced into the thermal constant by mere conditions of volume.

Detection of Circulating Tissue Factor and Factor VII in a Normal Population

1996 ◽  
Vol 75 (05) ◽  
pp. 772-777 ◽  
Author(s):  
Sybille Albrecht ◽  
Matthias Kotzsch ◽  
Gabriele Siegert ◽  
Thomas Luther ◽  
Heinz Großmann ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Normal Population ◽  
Mean Value ◽  
Factor Vii ◽  
Significant Difference ◽  
Age Dependent ◽  
The Mean ◽  
Highly Correlated ◽  
And Gender

SummaryThe plasma tissue factor (TF) concentration was correlated to factor VII concentration (FVIIag) and factor VII activity (FVIIc) in 498 healthy volunteers ranging in age from 17 to 64 years. Immunoassays using monoclonal antibodies (mAbs) were developed for the determination of TF and FVIIag in plasma. The mAbs and the test systems were characterized. The mean value of the TF concentration was 172 ± 135 pg/ml. TF showed no age- and gender-related differences. For the total population, FVIIc, determined by a clotting test, was 110 ± 15% and the factor VIlag was 0.77 ± 0.19 μg/ml. FVII activity was significantly increased with age, whereas the concentration demonstrated no correlation to age in this population. FVII concentration is highly correlated with the activity as measured by clotting assay using rabbit thromboplastin. The ratio between FVIIc and FVIIag was not age-dependent, but demonstrated a significant difference between men and women. Between TF and FVII we could not detect a correlation.

Determination of Plasminogen in Clots and Thrombi

1966 ◽  
Vol 16 (01/02) ◽  
pp. 038-050 ◽  
Author(s):  
Ulla Hedner ◽  
Inga Marie Nilsson ◽  
B Robertson
Keyword(s):  
Mean Value ◽  
Main Mechanism ◽  
Clot Lysis ◽  
Post Mortem ◽  
Digestion Time ◽  
Normal Volunteers ◽  
Casein Solution ◽  
The Mean

SummaryThe plasminogen content was determined by a casein method in plasma and serum from 20 normal volunteers. The mean plasminogen content was found to be 10.1 ACU (the arbitrary caseinolytic unit defined in such a way that using a 3% casein solution and a digestion time of 20 min. at 37°C, 10 ACU gave an extinction of 0.300). No difference between serum and plasma regarding the plasminogen content was found.Plasminogen was determined in drained and drained plus washed clots prepared from 2 ml plasma. The highest values found in the drained clots were 0.9 ACU/clot and 0.2 ACU/clot in the drained plus washed clots.Plasminogen was also determined in drained and drained plus washed clots prepared from plasma with added purified plasminogen. The plasminogen was recovered in the washing fluid. According to these tests, then, purified added plasminogen is washed out of the clots.The plasminogen content of 20 thrombi obtained post mortem was also determined. The mean value was found to be 0.7 ACU/cm thrombus. Judging from our results, the “intrinsic clot lysis theory” is not the main mechanism of clot dissolution.

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