The calculation of positive ancl negative spin densities in aromatic free radicals

1966 ◽  
Vol 19 (5) ◽  
pp. 897 ◽  
Author(s):  
FC Adam ◽  
WG Laidlaw
Keyword(s):  
Free Radicals ◽  
Spin Density ◽  
Excellent Agreement ◽  
Electron Spin ◽  
Simple Method ◽  
Unpaired Spin ◽  
Type Calculation ◽  
The Difference ◽  
Closed Shells ◽  
Spin Densities

A simple method of calculating the unpaired π electron spin density is proposed which equates the unpaired spin density to the difference between a density of n-1 electrons of a spin and a density of n electrons of β spin. The α spin density is found from an SCF-Pariser-Parr type calculation for 2(n+l) electrons in n + 1 closed shells and the β spin density from a calculation on 2n electrons in n, closed shells. Positive and negative spin densities are found which are in excellent agreement with experiment. These results are compared to spin densities calculated by other methods, and an improvement is noted in the representative cases considered.

scholarly journals Estimation of the Postmortem Duration of Mouse Tissue by Electron Spin Resonance Spectroscopy

2011 ◽  
Vol 2011 ◽  
pp. 1-11
Author(s):  
Shinobu Ito ◽  
Tomohisa Mori ◽  
Hideko Kanazawa ◽  
Toshiko Sawaguchi
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Spin Trap ◽  
Detection Sensitivity ◽  
Mouse Tissue ◽  
Spin Adduct ◽  
Simple Method ◽  
Oxidation Stress ◽  
Spin Resonance

Electron spin resonance (ESR) method is a simple method for detecting various free radicals simultaneously and directly. However, ESR spin trap method is unsuited to analyze weak ESR signals in organs because of water-induced dielectric loss (WIDL). To minimize WIDL occurring in biotissues and to improve detection sensitivity to free radicals in tissues, ESR cuvette was modified and used with 5,5-dimethtyl-1-pyrroline N-oxide (DMPO). The tissue samples were mouse brain, hart, lung, liver, kidney, pancreas, muscle, skin, and whole blood, where various ESR spin adduct signals including DMPO-ascorbyl radical (AsA∗), DMPO-superoxide anion radical (OOH), and DMPO-hydrogen radical (H) signal were detected. Postmortem changes in DMPO-AsA∗and DMPO-OOH were observed in various tissues of mouse. The signal peak of spin adduct was monitored until the 205th day postmortem. DMPO-AsA∗in liver (y=113.8–40.7 log (day),R1=-0.779,R2=0.6,P<.001) was found to linearly decrease with the logarithm of postmortem duration days. Therefore, DMPO-AsA∗signal may be suitable for detecting an oxidation stress tracer from tissue in comparison with other spin adduct signal on ESR spin trap method.

Effects of Polarization Function on the Spin Contamination and Distribution in β'- Me4P[Pd(dmit)2]2

2019 ◽  
Vol 966 ◽  
pp. 494-500
Author(s):  
Siti Nur Afifi Ahmad ◽  
Shukri Sulaiman ◽  
Lee Sin Ang ◽  
Isao Watanabe
Keyword(s):  
Electron Spin ◽  
Basis Sets ◽  
Cluster Method ◽  
Inhomogeneous Distribution ◽  
Doublet State ◽  
Polarization Function ◽  
Spin Contamination ◽  
The Difference ◽  
The One ◽  
Spin Densities

The effects of polarization function on the spin contamination and distribution in β'-Me4P[Pd(dmit)2]2 were studied using the DFT cluster method. Two basis sets, SV and SVP were considered in the calculations, where B3LYP functional was employed in the doublet state of the one-fragment and dimer clusters. The values of <S2> before annihilation for both SV and SVP basis sets are excellent and very close to the perfect theoretical eigenvalue of 0.75. The values of the spin densities at thiolate and thione calculated using SVP were found to be smaller than the ones using SV. The difference, however, is less than eight percent. In contrast, the difference in the spin density at Pd atoms in both monomers is significantly larger for the SVP, being about 21%. The inclusion of polarization function resulted in the shifting of electron density from the sulfur atoms to the central Pd atoms. The calculated spin densities revealed the inhomogeneous distribution of the electron spin in the dimer that leads to the existence of electron-rich and electron-poor regions.

Pump Performance Improvement by Restraining Back Flow in Screw-Type Centrifugal Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Yasushi Tatebayashi ◽  
Kazuhiro Tanaka ◽  
Toshio Kobayashi
Keyword(s):  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Simple Method ◽  
Back Flow ◽  
Pump Performance ◽  
Impeller Outlet ◽  
Pump Head ◽  
The Difference ◽  
Set Up

The authors have been investigating the various characteristics of screw-type centrifugal pumps, such as pressure fluctuations in impellers, flow patterns in volute casings, and pump performance in air-water two-phase flow conditions. During these investigations, numerical results of our investigations made it clear that three back flow regions existed in this type of pump. Among these, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. Thus the most important factor to achieve higher pump performance was to reduce the influence of this back flow. One simple method was proposed to obtain the restraint of back flow and so as to improve the pump performance. This method was to set up a ringlike wall at the suction cover casing between the impeller outlet and the volute casing. Its effects on the flow pattern and the pump performance have been discussed and clarified to compare the calculated results with experimental results done under two conditions, namely, one with and one without this ring-type wall. The influence of wall’s height on the pump head was investigated by numerical simulations. In addition, the difference due to the wall’s effect was clarified to compare its effects on two kinds of volute casing. From the results obtained it can be said that restraining the back flow of such pumps was very important to achieve higher pump performance. Furthermore, another method was suggested to restrain back flow effectively. This method was to attach a wall at the trailing edge of impeller. This method was very useful for avoiding the congestion of solids because this wall was smaller than that used in the first method. The influence of these factors on the pump performance was also discussed by comparing simulated calculations with actual experiments.

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