Dielectric Studies. Part XXXIV. Relaxation Evidence for Complex Formation of 1,4-Dioxan with Chelated Ring Systems

1972 ◽  
Vol 50 (17) ◽  
pp. 2799-2805 ◽  
Author(s):  
M. D. Magee ◽  
S. Walker
Keyword(s):  
Relaxation Time ◽  
Carbon Tetrachloride ◽  
Complex Formation ◽  
Loss Factor ◽  
Significant Interaction ◽  
Specific Interaction ◽  
Ring System ◽  
Dielectric Studies ◽  
Time Data ◽  
Microwave Frequencies

The dielectric constant (ε′) and loss factor (ε″) of solutions of (i) 8-hydroxyquinoline in cyclohexane, carbon tetrachloride, p-xylene and 1,4-dioxan, (ii) o-nitrophenol in n-heptane, cyclohexane, carbon tetrachloride, and 1,4-dioxan, (iii) 2,4-dinitrophenol in 1,4-dioxan, and (iv) 2,6-dinitrophenol also in 1,4-dioxan have been recorded at four microwave frequencies and at 25 °C. A comparison of the relaxation time data of 1-nitro-naphthalene with that of 8-hydroxyquinoline in a number of solvents indicates that a strong specific interaction occurs between the latter solute and the solvent 1,4-dioxan which leads to the formation of a complex. In addition, a comparative study of nitrobenzene and o-nitrophenol indicates a similar phenomenon. Strong interaction of the 1,4-dioxan with an atom or atoms in the chelated ring system appears to take place which produces a larger reorienting species than the solute molecule itself and appreciably lengthens the relaxation time, although the data do not establish the point of attachment of the 1,4-dioxan to the chelated ring. The complex formation is accompanied by an additional component to the dipole moment. For the dinitrophenols significant interaction with the solvent p-xylene complicates the interpretation of the relaxation time data, although in the 2,4-dinitrophenol the formation of a complex is indicated in 1,4-dioxan.

Dielectric Studies. Part XXXI. Analysis of the Dielectric Data of Phenol and its Polymerized Forms

1971 ◽  
Vol 49 (7) ◽  
pp. 1106-1114 ◽  
Author(s):  
M. D. Magee ◽  
S. Walker
Keyword(s):  
Dipole Moment ◽  
Relaxation Time ◽  
Mole Fraction ◽  
The State ◽  
Distribution Parameter ◽  
Dielectric Studies ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Dielectric Data ◽  
Intramolecular Process

The dielectric absorption and dispersions of several solutions of phenol in p-xylene have been measured at four microwave frequencies and at 2 MHz at a temperature of 25 °C. The data have been analyzed in terms of a mean relaxation time, a distribution parameter, and an apparent dipole moment which are useful empirical parameters for assessing the state of aggregation of the phenol molecules. The relaxation time at the lowest practicable concentration (0.02 mole fraction) is long for a molecule expected to relax predominantly by an intramolecular process. This and the behavior of the relaxation time and apparent dipole moment with increasing concentration are considered in terms of a model based on progressive association into an extended series of multimers, the trimer having a zero (or low) dipole moment and higher multimers becoming increasingly flexible.

Dielectric studies. Part XVIII. Dipole moments and relaxation times of some symmetrically substituted alkylbenzenes

1968 ◽  
Vol 46 (6) ◽  
pp. 847-851 ◽  
Author(s):  
J. Crossley ◽  
S. Walker
Keyword(s):  
Relaxation Time ◽  
Dipole Moments ◽  
Relaxation Times ◽  
Pure Liquid ◽  
Dielectric Studies ◽  
Molecular Reorientation ◽  
Microwave Frequencies ◽  
Short Relaxation Time ◽  
Dielectric Absorption ◽  
Liquid Benzene

The dielectric absorption at four microwave frequencies of pure liquid benzene and p-cymene at 25 °C, p-xylene and mesitylene at 25, 40, 50, and 60 °C, and solutions of durene and hexamethylbenzene in mesitylene at 60 °C has been examined. All show measurable loss factors and apparent dipole moments of about 0.1 to 0.2 D. These moments are less in magnitude than those associated with the short relaxation time (τ2) process for the polar monoalkylbenzenes. o-xylene and m-xylene. Their relaxation times are too short for molecular reorientation and there is a rough correlation between the number of collisions/molecule s and the reciprocal relaxation time.

Participation of the upstream region of the fibroin gene in the formation of transcription complex in vitro

1986 ◽  
Vol 6 (11) ◽  
pp. 3928-3933
Author(s):  
M Tsuda ◽  
S Hirose ◽  
Y Suzuki
Keyword(s):  
Complex Formation ◽  
Specific Interaction ◽  
Inhibitory Effect ◽  
Silk Gland ◽  
Upstream Region ◽  
Fibroin Gene ◽  
Transcription Complexes ◽  
Posterior Silk Gland

The addition of exogenous histones has an inhibitory effect on fibroin gene transcription in posterior silk gland extracts. The histones probably disturb a process in complex formation, because when transcription complexes were constructed by preincubation of the templates with the extracts, the inhibitory effect of histones was greatly reduced. Transcription of a fibroin gene construct, pFb5' delta-238, having the upstream region beyond the TATA box was relatively less inhibited than that of pFb5' delta-44 lacking the upstream region. This tendency toward differential inhibition was observed in the silk gland extracts but not in a HeLa cell extract and persisted even after complex formation in the silk gland extracts, suggesting a specific interaction of the upstream region with some factors in the extracts. The complexes formed on pFb5' delta-44 are probably more susceptible to the inhibitory effect of histones. On the basis of these results we propose a participation of the upstream region of the fibroin gene in the formation of stable transcription complexes at the promoter through an interaction with specific factors in the silk gland. Since the transcription-enhancing effect via the upstream region is augmented at a high histone/DNA ratio, it may mimic the in vivo situation in which the fibroin gene can be transcribed in the posterior silk gland even in the presence of excess suppressive materials.

COMPLEXES OF STANNIC IODIDE WITH AROMATIC HYDROCARBONS

1965 ◽  
Vol 43 (5) ◽  
pp. 1272-1278 ◽  
Author(s):  
J. F. Murphy ◽  
D. E. Baker
Keyword(s):  
Carbon Tetrachloride ◽  
Complex Formation ◽  
Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbons ◽  
Extinction Coefficient ◽  
Regular Solutions ◽  
Benzene Toluene ◽  
Yield Values ◽  
Complex Stabilities ◽  
Iodide Complex

Spectrophotometric measurements on solutions of stannic iodide were found to provide evidence for complex formation with aromatic hydrocarbons. Calculations, based on spectra for mixed solutions of benzene and stannic iodide in carbon tetrachloride, yield values of 0.26 for the equilibrium constant (mole fraction), 28 400 1/mole cm for the molar extinction coefficient of the benzene – stannic iodide complex. Kinetic evidence indicates that the order of decreasing complex stabilities is from xylene to toluene to benzene. The formation of stannic iodide – aromatic hydrocarbon complexes provides an explanation for the discrepancy between measured solubilities of stannic iodide in benzene, toluene, and xylene, and the solubilities predicted by the Hildebrand theory of regular solutions.

Differential Thermal Analysis and Dielectric Studies on Neopentanol under Pressure

1992 ◽  
Vol 47 (11) ◽  
pp. 1127-1134 ◽  
Author(s):  
H. G. Kreul ◽  
R. Waldinger ◽  
A. Würflinger
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Relaxation Time ◽  
Phase Transitions ◽  
Dielectric Relaxation ◽  
Pressure Dependence ◽  
Dielectric Relaxation Time ◽  
Dielectric Studies ◽  
Dielectric Measurements ◽  
Plastic Phase

Abstract Differential thermal analysis (DTA) and dielectric measurements have been performed on 2,2-dimethyl- 1-propanol (neopentanol) up to 200 MPa. Neopentanol exhibits at least one orientationally disordered (ODIC) phase (solid I) that transforms at lower temperatures to a non-plastic phase (solid II). There is evidence of a further ODIC phase denoted as solid I'. The pressure dependence of the phase transitions and the dielectric behaviour up to frequencies of 13 MHz are described. Activation enthalpies and volumes are derived from the dielectric relaxation time and compared with results for other alcohols

scholarly journals Studies on dielectric relaxation in relation to viscosity of some anilines, phenol, and their binary mixtures at microwave frequencies

2019 ◽  
Vol 97 (2) ◽  
pp. 210-215
Author(s):  
C.V. Maridevarmath ◽  
G.H. Malimath
Keyword(s):  
Relaxation Time ◽  
Steady State ◽  
Dynamic Viscosity ◽  
Room Temperature ◽  
Viscoelastic Model ◽  
Frictional Resistance ◽  
Nonlinear Behaviour ◽  
Viscoelastic Relaxation ◽  
Microwave Frequencies ◽  
Loss Formula

In the present work, the study of variation of relaxation time (τ) with viscosity of the medium (η) is carried out on four polar samples: 2-Nitroaniline, 4-Bromoaniline, 4-Chloroaniline, 4-Chlorophenol, and also on the binary mixture of 2-Nitroaniline + 4-Bromoaniline at room temperature by using microwave bench operating at a frequency of 9.59 GHz. In this regard, the different parameters like dielectric constant ([Formula: see text]), dielectric loss ([Formula: see text]), relaxation time (τs), macroscopic steady state viscosity (ηs), dynamic viscosity (ηd), and viscoelastic relaxation time (τve) were determined for all the systems. It is observed that the relaxation time (τs) increases with the increase in the viscosity of the medium for all the systems. Plots of log(τs) versus log(ηs) for all the systems show that variation of relaxation time is found to be nonlinear in the higher viscosity regions. This suggests the failure of Debye’s theory at these regions. Further, the nonlinear behaviour of relaxation time with the viscosity is explained by using the viscoelastic model suggested by Barlow et al. (Proc. R. Soc. A 309, 473 (1969). doi: 10.1098/rspa.1969.0053 ). It is also observed that macroscopic steady state viscosity (ηs) values are greater than the dynamic viscosity (ηd), and viscoelastic relaxation time (τve) values were found to be lower compared to the relaxation time (τs). These results suggest that the effective frictional resistance experienced by the molecules during reorientation is lower and the measured values of macroscopic steady state viscosity (ηs) are frequency dependent.

scholarly journals Dielectric Behaviour of Zn/Al-NO3LDHs Filled with Polyvinyl Chloride Composite at Low Microwave Frequencies

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Ethar Y. Salih ◽  
Zulkifly Abbas ◽  
Samer Hasan Hussein Al Ali ◽  
Mohd Zobir Hussein
Keyword(s):  
Dielectric Properties ◽  
Polyvinyl Chloride ◽  
Loss Factor ◽  
Room Temperature ◽  
Dielectric Measurements ◽  
X Ray Diffraction ◽  
Microwave Frequencies ◽  
X Ray ◽  
Essential Properties ◽  
Double Hydroxide

Recently, researchers have shown great interest in improving the thermal, mechanical, dielectric, and microwave properties of pure polymers through the use of polymer-based composites. The essential properties of polymer-based composites can be modified by varying the amount of Zn/Al-NO3layered double hydroxide (LDH) added to polyvinyl chloride (PVC). Therefore, by determining the optimal ratio of LDH in the PVC matrix, the dielectric properties of PVC-LDH composites can be improved. An LDH was prepared using the coprecipitation method, while PVC-LDH composites were prepared using tetrahydrofuran (THF) as the solvent. The composites were characterised using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), and room temperature dielectric measurements were investigated using an RF Impedance/Material Analyzer (Agilent 4291). The results confirmed that the prepared composites were pure. Additionally, the presence of LDH in the PVC matrix was verified. The dielectric measurements showed that an increase in the LDH concentration leads to an increase in the dielectric constant and the dielectric loss factor. When used as dielectric filler in the PVC matrix, the LDH improved the dielectric properties of the fabricated composites. The results indicate that these composites show great potential for use as microwave absorbers at low microwave frequencies.

Pulsed Doppler assessment of left ventricular diastolic function in normal and cardiomyopathic cats

1999 ◽  
Vol 35 (4) ◽  
pp. 285-291 ◽  
Author(s):  
JM Bright ◽  
ME Herrtage ◽  
JF Schneider
Keyword(s):  
Relaxation Time ◽  
Diastolic Function ◽  
Peak Velocity ◽  
Left Ventricular Diastolic Function ◽  
Left Ventricular ◽  
P Value ◽  
Pulsed Doppler ◽  
Time Data ◽  
Isovolumic Relaxation Time ◽  
Isovolumic Relaxation

Left ventricular (LV) diastolic function was evaluated in 16 cats with primary hypertrophic cardiomyopathy (HCM) using pulsed Doppler (PD) assessment of transmitral flow and isovolumic relaxation time. Data obtained was compared to data from 12 healthy, adult, research cats. Compared to normal cats, the HCM group showed significantly (p value less than 0.05) reduced early LV inflow velocities (mean +/- standard error [SE], peak velocity of 0.70+/-0.04 m/s versus 0.54+/-0.04 m/s and integrated velocity of 0.48+/-0.08 m/s versus 0.37+/-0.03 m/s); a reduced rate of deceleration of early inflow (mean+/-SE, -12.0+/-1.0 m/s2 versus -5.1+/-1.1 m/s2); prolonged isovolumic relaxation time (mean +/- SE, 45.7+/-3.3 ms versus 76.0+/-3.1 ms); and increased atrial systolic flow velocities (mean +/- SE, peak velocity of 0.29+/-0.04 m/s versus 0.48+/-0.04 m/s and integrated velocity of 0.21+/-0.03 m/s versus 0.34+/-0.03 m/s). The results suggest that PD provides a noninvasive method of identifying and quantifying functional diastolic impairment in cats with HCM.

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