Search results for "Ion temperature"
showing 10 items of 220 documents
Positronium as a probe in natural polymers: decomposition in starch
2009
Ortho-positronium (o-Ps) is used as a probe in positron annihilation lifetime spectroscopy (PALS) experiments, to characterise the behaviour of free volumes in natural starch samples, as a function of temperature (T). Up to about 540 K, the o-Ps intensity, I(3), remains constant at 26.2% while its lifetime, tau(3), is found to increase linearly. Both parameters undergo a decrease above this T, due to the onset of decomposition, which results in a shrinking of the sample pellets. The results indicate that the glass transition temperature should be above 501 K. Data from thermal gravimetry analysis (TGA) measurements are well described by supposing a first order process for the survival proba…
Transesterification of rapeseed oil over acid resins promoted by supercritical carbon dioxide
2011
The methanolysis of rapeseed oil catalyzed by commercial styrene-divinylbenzene macroporous acid resins was performed in a batch reactor at 100-140 °C and 10-46 MPa to study the effect of supercritical carbon dioxide (scCO2) on the performances of the process. Reaction temperatures of 120-140 °C were necessary to obtain high enough yields of fatty acid methyl esters. Upon addition of scCO2 faster transesterification kinetics was obtained also at the lowest investigated operating pressure (10-11 MPa), working in two fluid phase systems. Experiments performed changing the reaction time indicated that most of the esters were formed during the first 3 h. When the pressure was increased at 38-46…
Study of a new direct current atmospheric pressure glow discharge in helium
2011
Abstract In this study a new DC-APGD operated in He was developed and characterized. The discharge is operated at 0.9 kV and about 25–35 mA and at a gas flow of 100 ml/min. The source was spectroscopically studied and parameters such as the rotational temperature (Trot), the excitation temperature (Texc), the ionization temperature (Tion) and the electron number density (ne) were determined. The current–voltage characteristic of the source was studied as well. At optimized conditions the discharge operates in the normal region of the current–voltage characteristic. Rotational and excitation temperatures determined with the use of OH band and Fe I lines as thermometric species were of the or…
Investigation of the effect of intensive milling in a planetary ball mill on the thermal decomposition of basic nickel carbonate
2011
The kinetics of thermal decomposition of basic nickel carbonate NiCO3Ni?(OH)2?nH2O and the effect of intensive milling in a planetary ball mill on its parameters, have been investigated. The values of the reaction heat and of the activation energy of thermal decomposition have been determined. Investigations of the thermal decomposition of the products of ball milling of investigated compound revealed a distinct effect of milling on the reaction temperature and heat consumed during the thermal decomposition of investigated compound.
Investigation of the effect of intensive ball milling in a planetary ball mill on the thermal decomposition of cadmium carbonate and basic zinc carbo…
2007
The kinetics of thermal decomposition of cadmium carbonate CdCO3 and basic zinc carbonate ZnCO3?nZn(OH)2 and the effect of intensive milling in a planetary ball mill on its parameters, have been investigated. The values of the reaction heat and of the activation energies of thermal decomposition have been determined for both the compounds. Investigations of the thermal decomposition of the products of ball milling of investigated compounds revealed a slight effect of milling conditions on the reaction temperature and heat consumed during the thermal decomposition of ZnCO3?nZn(OH)2. No effect of ball milling on the thermal decomposition of CdCO3 has been found.
Pressure effect on temperature induced high-spin–low-spin phase transitions
2002
The effect of hydrostatic pressure on the transition temperature and the hysteresis widths of first-order spin crossover phase transitions is considered in the frame of the mean field theory and on the basis of the scope of recent pressure experiments. Relevant parameters for a qualitative description of the behaviour of spin transition compounds under pressure are derived and analysed.
Synthesis of 2-anilinobenzimidates, anthranilamides, and 2,3-dihydroquinazolin-4(1H)-ones from N-heterocyclic carbenes of indazole
2015
N-Heterocyclic carbenes of indazole (indazol-3-ylidenes), which are substituted at N1 with aromatics were generated in situ from the corresponding indazolium salts. At 60 °C the indazol-3-ylidenes underwent a ring-opening under N–N bond cleavage to intermediary N-(6-methylenecyclohexa-2,4-dien-1-ylidene)anilines. Trapping of these intermediates by alcohols proved to be a convenient method for the preparation of 2-anilinobenzimidates, which have scarcely been described in the literature. The reaction temperature avoids carbene dimerization, which occurs at −80 °C or rearrangement of the ring-opened intermediate to acridines, which affords 100 °C. Water converted the ring-opened products into…
Photochemical electrocyclisation of 3-vinylindoles to pyrido[2,3-a]-, pyrido[4,3-a]- and thieno[2,3-a]-carbazoles: Design, synthesis, DNA binding and…
2009
In the context of the design and synthesis of DNA ligands, some new hetarene annelated carbazoles were synthesized. As lead structure the intercalating tetracyclic systems pyrido[2,3-a]- and pyrido[4,3-a]-carbazoles and in one case a thieno[2,3-a]-carbazole were taken into account. A dialkyl amino amidic chain was introduced to the planar chromophoric system with the intent to generate minor groove binding properties. The cytotoxicity of some compounds was examined by the NCI antitumor screening. Furthermore, biophysical as well as biochemical studies were performed in order to get some information about the DNA-binding properties and inhibition of DNA related functional enzymes of this new…
Cooperativity in the Iron(II) Spin-Crossover Compound [Fe(ptz)6](PF6)2 under the Influence of External Pressure (ptz = 1-n-Propyltetrazole)
1997
The iron(II) spin-crossover compound [Fe(ptz)(6)](PF(6))(2) (ptz = 1-propyltetrazole) crystallizes in the triclinic space group Ponemacr;, with a = 10.6439(4) Å, b = 10.8685(4) Å, c = 11.7014(4) Å, alpha = 75.644(1) degrees, beta = 71.671(1) degrees, gamma = 60.815(1) degrees, and Z = 1. In [Fe(ptz)(6)](PF(6))(2), the thermal spin transition is extremely steep because of cooperative effects of elastic origin. The transition temperature at ambient pressure is 74(1) K. An external pressure of 1 kbar shifts the transition temperature to 102(1) K, corresponding to a stabilization of the low-spin state, which is smaller in volume. The volume difference between the high-spin and the low-spin stat…
Electronic Relaxation Phenomena Following 57Co(EC)57Fe Nuclear Decay in [MnII(terpy)2](ClO4)2·1/2H2O and in the Spin Crossover Complexes [CoII(terpy)…
2001
The valence states of the nucleogenic 57Fe arising from the nuclear disintegration of radioactive 57Co by electron capture decay, 57Co(EC)57Fe, have been studied by Mossbauer emission spectroscopy (MES) in the 57Co-labeled systems: [57Co/Co(terpy)2]Cl2·5H2O (1), [57Co/Co(terpy)2](ClO4)2·1/2H2O (2), and [57Co/Mn(terpy)2](ClO4)2· 1/2H2O (3) (terpy = 2,2‘:6‘,2‘ ‘-terpyridine). The compounds 1, 2, and 3 were labeled with ca. 1 mCi of 57Co and were used as the Mossbauer sources at variable temperatures between 300 K and ca. 4 K. [Fe(terpy)2]X2 is a diamagnetic low-spin (LS) complex, independent of the nature of the anion X, while [Co(terpy)2]X2 complexes show gradual spin transition as the temp…