scholarly journals Studies on Polydisperse Systems Using an Air-Driven Ultracentrifuge: Application to Phosphatidylcholine Vesicles

1979 ◽  
Vol 32 (2) ◽  
pp. 187 ◽  
Author(s):  
RG Clarke ◽  
GR Eagle ◽  
GJ Howlett
Keyword(s):  
Molecular Weight ◽  
Specific Volume ◽  
High Speed ◽  
Theoretical Calculations ◽  
Analytical Ultracentrifuge ◽  
Solution Density ◽  
Good Agreement

A high-speed air-driven ultracentrifuge (Airfuge) has been used to determine the molecular weight and effective specific volume of phosphatidylcholine vesicles. The method used to determine the effective specific volume involved varying the solution density until zero sedimentation of the vesicles occurred. The value obtained for the effective specific volume of 0�9885 mlJg agrees well with previously reported values. The determination of the molecular weight of the vesicles is based on a method in which the fraction of vesicles remaining in an upper fraction of the solution column is compared with the values obtained using standard proteins. The values obtained for the molecular weight of the vesicles range from 1� 7 x 106 to 2�3 X 106 and are in good agreement with results obtained using the analytical ultracentrifuge and with previously reported results. Possible effects due to the polydispersity of the solute are assessed using theoretical calculations and the possibility of using the Airfuge for the study of other polydisperse systems is discussed.

Measurement of the Isothermal Volume Dilation Accompanying the Unilateral Extension of Rubber

1959 ◽  
Vol 32 (2) ◽  
pp. 428-433
Author(s):  
Fred G. Hewitt ◽  
Robert L. Anthony
Keyword(s):  
Molecular Weight ◽  
Young’S Modulus ◽  
Experimental Results ◽  
Molecular Weights ◽  
Rubber Specimen ◽  
A Value ◽  
Fractional Increase ◽  
Internal Agreement ◽  
Good Agreement

Abstract The fractional increase in volume accompanying the isothermal extension of soft gum rubber was measured for four rubber samples at mean extensions of 14, 33, and 51%. The chain molecular weights Mc of the four samples were 5500, 5100, 4400, and 3000, with an estimated uncertainty of about 10% in each value of Mc. The observed fractional increase in volume ranged from 3.2×10−5 to 142×10−5, the latter value being observed for the sample of lowest chain molecular weight and at the extension of 51%. The experimental results for each sample have been represented by theoretical curves based on Gee's expression for the fractional increase in volume as a function of the sample extension. The theoretical curves exhibit good agreement with those of Gee, Stern, and Treloar. The process of fitting the theoretical curves to the experimental points constituted a determination of Young's modulus E for each rubber specimen. As a check on the experimental results, and also on the theory employed, determinations of E were also made by two additional methods, namely, from rough stess-strain curves, and from the relation E=3γρRT/Mc. With one exception, the internal agreement between the three determinations of E for the four different samples was satisfactory. The exception noted can probably be ascribed to the use of too small a value of Mc for the sample of lowest chain molecular weight.

scholarly journals Development and Determination of the Parameters of a Capacitive Seed Sowing Sensor for Row Crops

2019 ◽  
Vol 13 (2) ◽  
pp. 4-9 ◽  
Author(s):  
Anatoliy I. Zavrazhnov ◽  
Yakov P. Lobachevskiy ◽  
Nikita Yu. Pustovarov
Keyword(s):  
Travel Time ◽  
High Speed ◽  
Theoretical Calculations ◽  
Software Systems ◽  
Sensitive Area ◽  
Laboratory Studies ◽  
Electrical Parameters ◽  
Row Crops ◽  
Seed Sowing

Abstract. The development of a universal control system requires designing unified seed sowing sensors that allow controlling the sowing of seeds of different crops. (Research purpose) To provide theoretical grounds for the determination of parameters and installation location of a capacitive seeding sensor. (Materials and methods) In the course of the study, the authors have made theoretical calculations of the seed travel trajectories in mechanical and pneumatic sowing machines using the Mathcad and Microsoft Excel software systems, at various sowing machine frequencies: 11.5; 17.5 and 26.0 revolutions per minute as well as the calculation of the electrical parameters of the designed seeding sensor. Laboratory studies of the trajectory have been performed at the same rotational speeds of the sowing unit disc using high-speed seeding surveys on an experimental installation with subsequent processing of the obtained video materials. The optimum installation angle of the sensor has been experimentally studied from 0 to 67.5 degrees with a pace of 22.5 degrees to minimize the travel time of seeds through the sensitive area of the sensor, and as a result, to increase the sensor resolution using the developed software. (Results and discussion) Geometric and electrical parameters of the designed sowing sensor have been obtained, and its optimum location has been determined. (Conclusions) In the course of laboratory studies, data similar to the calculation results have been obtained; the relative value of the convergence coefficient between experimentally obtained and theoretical indicators does not exceed 0,55, provided these values are obtained at a distance less than the radius of seeds. The authors have experimentally determined the minimum distance between the sensor plates, which amounts to 20 millimetre, and calculated the electrical parameters of the sensor. They have also stated that the height of the sensitive zone should be at least 5 millimeters for reliable metering of individual seeds under these conditions. The obtained data allowed designing an experimental seeding sensor to determine the optimum angle and the sensor installation site. It has been concluded, that in order to minimize the travel time of seeds in the sensitive area of the sensor, the latter should be installed perpendicularly to the flight trajectory of the seeds.

Natural width and Doppler broadening in the 152 Sm 961 keV γ -ray resonance

1960 ◽  
Vol 257 (1288) ◽  
pp. 44-51 ◽  
Keyword(s):  
Fluorescence Intensity ◽  
Resonance Line ◽  
High Speed ◽  
Theoretical Calculations ◽  
Doppler Broadening ◽  
Resonance Fluorescence ◽  
Natural Width ◽  
Natural Line Width ◽  
Γ Ray ◽  
Good Agreement

By moving a 152m Eu 2 O 3 source on the tips of a high-speed rotor, the 961 keV emission spectrum has been swept across the resonance line of a stationary Sm 2 O 3 scatterer. The observed resonance/fluorescence intensity has been compared with a curve calculated by taking into account the Doppler effects due to electron capture and thermal motions but neglecting the effects of natural line widths. At negative rotor speeds, when the emission line scans the low-energy wing of the resonance line, the influence of the natural line width on the resonance/fluorescence intensity has been observed. At positive rotor speeds there is a good agreement with the theoretical calculations; this shows that with a stationary source the thermal broadening is dominant in restoring the resonance whereas the line wing overlap is negligible.

Revisiting cross sections for proton induced reactions on natural lead between 10 and 80 MeV

2021 ◽  
Vol 109 (4) ◽  
pp. 233-242
Author(s):  
Salim Gülez ◽  
Bhawna Pandey ◽  
Erik Strub
Keyword(s):  
Cross Sections ◽  
Additional Data ◽  
Historical Data ◽  
Theoretical Calculations ◽  
Historical Record ◽  
High Proton ◽  
Γ Ray ◽  
Proton Induced Reactions ◽  
Good Agreement

Abstract This work is focused on the natPb(p,xn)207Bi reaction to extend earlier works on proton induced reactions for the determination of cross sections of residual nuclides. 207Bi decay (half-life 31.55 years) was measured by γ-ray spectrometry in 42 lead foils which had been irradiated by high proton fluxes 20 years ago. Since then, all short-lived radionuclides produced during the irradiation have decayed, so the background is strongly reduced and the cross section could be measured more precisely than during the original measurements. The results are found to be in very good agreement with the historical record. Additionally, theoretical calculations with modern Monte Carlo based codes were performed to compare the calculations of various Bi, Tl and Pb reactions with the historical data and with additional data from literature. The deviations of the new data from both theoretical calculations using EMPIRE and TALYS are discussed.

scholarly journals Theoretical Determination of Porpoising Instability of High-Speed Planing Boats

1978 ◽  
Vol 22 (01) ◽  
pp. 32-53 ◽  
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Theoretical Method ◽  
Theoretical Determination ◽  
Damping Characteristics ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Good Agreement

A theoretical method is derived for predicting trim angle and speed coefficient at the inception of propoising of prismatic planing hulls. Although equations are derived for the surge, pitch, and heave degrees of freedom, it is seen that the effect of surge is small at ordinary operating trim angles. Comparisons of theoretical predictions with existing experimental data on coupled pitch and heave porpoising show reasonably good agreement for a wide range of speed coefficients, load coefficients, and deadrise angles. The theory may also be used for estimating the natural frequencies and damping characteristics of prismatic hulls in the stable, high-speed planing range.

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