Home About us Contact
|
Home About us Contact | ||
|
|
||
Liquid State (liquid + state)
Selected AbstractsNMR methods for studying membrane-active antimicrobial peptidesCONCEPTS IN MAGNETIC RESONANCE, Issue 2 2004Erik Strandberg Abstract NMR is a versatile tool for studying interactions between antimicrobial peptides and lipid membranes. Different approaches using both liquid state and solid state NMR are outlined here, with an emphasis on solid state NMR methods, to study the structures of antimicrobial peptides in lipid bilayers as well as the effect of these peptides on model membranes. Different NMR techniques for observing both peptides and lipids are explained, including 2H, 13C, 15N, and 19F labels, or natural abundance 1H, 13C, or 31P. Previous studies in the field are extensively reviewed in easily accessible tables. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 23A: 89,120, 2004. [source] Survey of Theoretical Work for the Proposed HEDgeHOB Experimental Schemes: HIHEX and LAPLASCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4-5 2007N. A. Tahir Abstract This paper presents a review of the theoretical work that has resulted in a scientific proposal on studies of High-Energy-Density (HED) states in matter using intense beams of energetic heavy ions that will be available at the future Facility for Antiprotons and Ion Research (FAIR) at Darmstadt [W.F. Henning, Nucl. Inst. Meth B 24 (2003) 725-729]. The proposal is named HEDgeHOB that stands for High Energy Density Matter Generated by Heavy Ion Beams. Two experimental schemes have been worked out for the HEDgeHOB experimental proposal, namely, HIHEX and LAPLAS. The first scheme allows for studies of HED states by isochoric and uniform heating of matter by an intense heavy ion beam that is followed by isentropic expansion of the heated material. Numerical simulations have shown that using the beam parameters that will be available at the FAIR, one can access all the interesting physical states of HED matter including an expanded hot liquid state, twophase liquid-gas region, critical point parameters and strongly coupled plasmas for all the materials of interest. The second scheme involves a low-entropy compression of a test material like hydrogen that is enclosed in a cylindrical shell of a high-Z material like gold or lead. The target can be driven by a hollow or a circular beam. This compression scheme relies on multiple shock reflection between the hydrogen-gold (lead) boundary and the cylinder axis. The hydrodynamic stability of the LAPLAS target has also been analyzed that shows that the implosion is completely stable to Rayleigh-Taylor and Richtmyer-Meshkov instabilities. LAPLAS implosion using a hollow beam is suitable for studying the problem of hydrogen metallization whereas the one employing a circular focal spot leads to physical conditions that are expected to exist in the interiors of the giant planets. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Raman and Rayleigh scattering study of crystalline polyoxyethyleneglycolsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005M. Kozielski Abstract Results of the study of Raman and Rayleigh scattering in crystalline polyoxyethyleneglycols (PEG) and PEG 1500 aqueous solution are reported. The conformational changes of the polymer chain have been studied as a function of PEG water solution concentration and molecular weight. Intensity ratios of the gauche and trans conformation around C,C and C,O bonds have been estimated from the Raman spectra. Moreover, from the Raman band parameters the values of the order parameters versus aqueous solution concentration have been determined. The influence of an external electric field on these parameters has been analysed. Mutual orientation of polyoxyethyleneglycol chains in the crystalline and liquid state has been studied on the basis of the angular correlation parameters obtained from the Rayleigh band intensity as a function of aqueous solution concentration and molecular weight. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Principal features of impact-generated hydrothermal circulation systems: mineralogical and geochemical evidenceGEOFLUIDS (ELECTRONIC), Issue 3 2005MIKHAIL V. NAUMOVArticle first published online: 14 JUL 200 Abstract Any hypervelocity impact generates a hydrothermal circulation system in resulting craters. Common characteristics of hydrothermal fluids mobilized within impact structures are considered, based on mineralogical and geochemical investigations, to date. There is similarity between the hydrothermal mineral associations in the majority of terrestrial craters; an assemblage of clay minerals,zeolites,calcite,pyrite is predominant. Combining mineralogical, geochemical, fluid inclusion, and stable isotope data, the distinctive characteristics of impact-generated hydrothermal fluids can be distinguished as follows: (i) superficial, meteoric and ground water and, possibly, products of dehydration and degassing of minerals under shock are the sources of hot water solutions; (ii) shocked target rocks are sources of the mineral components of the solutions; (iii) flow of fluids occurs mainly in the liquid state; (iv) high rates of flow are likely (10,4 to 10,3 m s,1); (v) fluids are predominantly aqueous and of low salinity; (vi) fluids are weakly alkaline to near-neutral (pH 6,8) and are supersaturated in silica during the entire hydrothermal process because of the strong predominance of shock-disordered aluminosilicates and fusion glasses in the host rocks; and (vii) variations in the properties of the circulating solutions, as well as the spatial distribution of secondary mineral assemblages are controlled by tempera ure gradients within the circulation cell and by a progressive cooling of the impact crater. Products of impact-generated hydrothermal processes are similar to the hydrothermal mineralization in volcanic areas, as well as in modern geothermal systems, but impacts are always characterized by a retrograde sequence of alteration minerals. [source] Molecular dynamics simulations of hydrotropic solubilization and self-aggregation of nicotinamideJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2010Yong Cui Abstract Hydrotropy is a phenomenon where the presence of a large quantity of one solute enhances the solubility of another solute. The mechanism of this phenomenon remains elusive and a topic of debate. This study employed molecular dynamics simulation to investigate the hydrotropic mechanism of a model system consisting of a hydrotropic agent, nicotinamide (NA), a poorly water-soluble solute, PG-300995 (PG), and water. Our study demonstrates that NA and PG undergo significant aggregation in the aqueous solution, a result correlating closely to the self-aggregation of NA under the same conditions. The correlations are found both structurally and dynamically, suggesting that the self-aggregation of NA may be a prerequisite, or at least a major contributor, to its hydrotropic effects. The self-aggregation of NA allows the segregation of the hydrophobic solute from water, a key step to ease the energy increase to the system. Energetic evidences directly show that the hydrotropic solubilization is favored in the presence of NA aggregation. These results are in strong support of the molecular aggregation hypothesis for hydrotropic solubilization. Additionally, it is found that the restoration of water,water HBs from the interference of the NA and PG molecules plays an important role for the aggregation. The HBs between the solute and the hydrotrope may contribute, but is not vital, to the aggregation and hence the hydrotropic effects. The dynamic data confirm that the aggregates, while remain in liquid state, are much more active dynamically than a pure NA amorphous/liquid phase under the same temperature and pressure. By equilibrating an NA amorphous agglomerate with water, it is found that the aggregation state, rather than an NA,water two phase system, is the equilibrium state of the NA,+,water system. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3048,3059, 2010 [source] Anomalous concentration dependence of the coordination behavior of Cl, ion to Ln3+ ion (Ln3+ = rare-earth ion) in anhydrous LnCl3 alcohol solutionsJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2007Y. Yoshimura Abstract Raman spectroscopic measurements were carried out for the anhydrous LnCl3·20ROH·XLiCl solutions (Ln3+ = La3+, Lu3+, X = 0,3; ROH = MeOH, EtOH, n -PrOH) in the liquid state. The salt concentration (X) dependence of the wavenumber for the Ln,Cl stretching Raman band (,Ln,Cl) is examined in conjunction with the formation of chloro-rare-earth complexes. We have obtained very intriguing results including the fact that the chloro complexations of the middle rare-earth ions (e.g. gadolinium, holmium ions, etc.) in the MeOH and EtOH solutions show peculiar behavior with regard to the salt concentration dependence: the ,Ln,Cl wavenumber increases with the increasing chloride concentration. However, the ,Ln,Cl wavenumbers of the light and heavy rare-earth (e.g. lanthanum, lutetium, etc.) salt solutions show normal behavior; i.e. ,Ln,Cl decreases with the increasing chloride concentration. On the other hand, in the n -PrOH solutions, the ,Ln,Cl frequency in the solutions of all the rare-earth elements exhibits a normal behavior. We now present a possible mechanism for this anomalous concentration dependence of coordination of Cl, ions to Ln3+ ions in anhydrous LnCl3 alcohol solutions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Vibrational spectroscopic studies, conformations and quantum chemical calculations of 3,3,3-trifluoropropyl- silane and 3,3,3-trifluoropropylsilane- d3,JOURNAL OF RAMAN SPECTROSCOPY, Issue 1-3 2006Peter Klaeboe Abstract Infrared spectra of 3,3,3-trifluoropropylsilane (CF3CH2CH2SiH3) and 3,3,3-trifluoropropylsilane- d3 (CF3 CH2CH2SiD3) were obtained in the vapour, liquid, and crystalline solid phases in the range 4000,50 cm,1. Additional spectra in argon matrices at 5 K were recorded before and after annealing to temperatures 20,34 K. Raman spectra of the compounds as liquids were recorded at various temperatures between 296 and 183 K and spectra of the amorphous and crystalline solids were obtained. The spectra revealed the existence of two conformers (anti and gauche) in the fluid phases and in the matrices. When the two vapours were shock-frozen on a cold finger at 78 K, they turned partly crystalline immediately. After subsequent annealing to 140,150 K, ca 7,9 Raman bands of both molecules present in the liquids vanished in the crystal. Similar variations in intensity were observed in the corresponding infrared spectra before and after annealing. The spectra revealed the existence of one conformer (anti) in the crystal. From Raman intensity variations of three independent pairs of anti and gauche bands between 298 and 173 K for the parent compound, and 298 and 183 K for the deuterated analogue, the values ,confHo(gauche,anti) = 4.1 ± 0.3 kJ mol,1 for the parent compound and the same value for the deuterated species were obtained in the liquid state. Annealing experiments in the matrices show that the gauche bands vanish after annealing, demonstrating that the anti conformer also has the lower energy here and that the barrier to gauche , anti inter-conversion is around 5,6 kJ mol,1. The spectra of both conformers have been interpreted in detail. Ab initio and DFT calculations at the HF/6,311G**, B3LYP/6,311 G** and MP2/6,311 G** levels gave optimized geometries, infrared and Raman intensities and vibrational wavenumbers for the anti and gauche conformers. The conformational enthalpy difference derived from the calculations was between 6.0 and 4.1 kJ mol,1 with anti being the low energy conformer. Copyright © 2006 John Wiley & Sons, Ltd. [source] A Nonequilibrium Statistical Mechanical Model of Structural Relaxation in GlassJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006John C. Mauro We derive a new model of structural relaxation in glass based on nonequilibrium statistical mechanics and the Stillinger model of inherent structures. Our model follows the evolution of a system from its equilibrium liquid state through an arbitrary cooling path and allows for the computation of macroscopic properties as a function of time. Using this new model, we have numerically demonstrated for the first time the connection between the topography of a potential energy landscape in 1-D and its corresponding fragility. [source] Strontium Dialuminate SrAl4O7: Synthesis and StabilityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2002Mickaël Capron Up to now, strontium dialuminate, SrAl4O7 (SA2), could be synthesized only by solidification from the high-temperature liquid state. We describe its synthesis from a spray-dried amorphous precursor, and specify its stability domains. Its kinetics of formation is very low. It can be crystallized in the 900,1000°C temperature range either directly with a low heating rate or via two metastable solid solutions,hexagonal strontium monoaluminate (SrAl2O4 (SA)) and ,-alumina,by annealing at 950,1000°C. As the temperature is raised beyond 1100°C, SA2 becomes metastable, its formation is no longer possible, and the crystallization of Sr4Al14O25 (S4A7) is favored. The latter compound, whose composition is close to that of SA2, is stable up to 1500°C. At higher temperature it decomposes into SA and SA2, which in its turn decomposes into SA and SA6 (SrAl12O19). There is again another stability domain for SA2, restricted to a narrow temperature scale close to its melting point (,1800°C). The behaviors at crystallization from amorphous precursors at low temperature and from liquid at very high temperature are symmetrical: low heating or cooling rates produce pure SA2 while too rapid kinetics result in mixtures of phases. [source] Co-acquisition of hyperpolarised 13C and 15N NMR spectraMAGNETIC RESONANCE IN CHEMISTRY, Issue 12 2007Iain J. Day Abstract Recent developments in dynamic nuclear polarisation now allow significant enhancements to be generated in the cryo solid state and transferred to the liquid state for detection at high resolution. We demonstrate that the Ardenkjaer,Larsen method can be extended by taking advantage of the properties of the trityl radicals used. It is possible to hyperpolarise 13C and 15N simultaneously in the solid state, and to maintain these hyperpolarisations through rapid dissolution into the liquid state. We demonstrate the almost simultaneous measurement of hyperpolarised 13C and hyperpolarised 15N NMR spectra. The prospects for further improvement of the method using contemporary technology are also discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Generation and interrogation of a pure nuclear spin state by parahydrogen-enhanced NMR spectroscopy: a defined initial state for quantum computationMAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2005D. Blazina Abstract We describe a number of studies used to establish that parahydrogen can be used to prepare a two-spin system in a pure state, which is suitable for implementing NMR quantum computation. States are generated by pulsed and continuous-wave (CW) UV laser initiation of a chemical reaction between Ru(CO)3(L2) [where L2 = dppe = 1,2-bis(diphenylphosphino)ethane or L2 = dpae = 1,2-bis(diphenylarsino)ethane] with pure parahydrogen (generated at 18 K). This process forms Ru(CO)2(dppe)(H)2 and Ru(CO)2(dpae)(H)2 on a sub-microsecond time-scale. With the pulsed laser, the spin state of the hydride nuclei in Ru(CO)2(dppe)(H)2 has a purity of 89.8 ± 2.6% (from 12 measurements). To achieve comparable results by cooling would require a temperature of 6.6 mK, which is unmanageable in the liquid state, or an impractical magnetic field of 0.44 MT at room temperature. In the case of CW initiation, reduced state purities are observed due to natural signal relaxation even when a spin-lock is used to prevent dephasing. When Ru(CO)3(dpae) and pulsed laser excitation are utilized, the corresponding dihydride product spin state purity was determined as 106 ± 4% of the theoretical maximum. In other words, the state prepared using Ru(CO)3(dpae) as the precursor is indistinguishable from a pure state. Copyright © 2004 John Wiley & Sons, Ltd. [source] Local existence of solutions of a three phase-field model for solidificationMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 12 2009Bianca Morelli Calsavara Caretta Abstract In this article we discuss the local existence and uniqueness of solutions of a system of parabolic differential partial equations modeling the process of solidification/melting of a certain kind of alloy. This model governs the evolution of the temperature field, as well as the evolution of three phase-field functions; the first two describe two different possible solid crystallization states and the last one describes the liquid state. Copyright © 2008 John Wiley & Sons, Ltd. [source] Condensate's prospects boosted by shortage of light crudeOIL AND ENERGY TRENDS, Issue 11 2005Article first published online: 14 NOV 200 Rapidly rising demand for light, low sulphur refined products such as gasoline and diesel is causing refiners to take an increasing interest in condensate. Condensate is principally a by-product of natural gas production and has long been seen as an awkward product to extract and market. It has to be separated from the gas as well as being sold and marketed separately. It sometimes requires specialist storage and handling in order to maintain it in a liquid state. [source] The recovery of the shear viscosity of thermally aged bulk and ribbon glassy Pd40Cu30Ni10P20 by rapid quenching from the supercooled liquid statePHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 2-3 2009V. A. Khonik Abstract Isochronal (= linear heating) measurements of the shear viscosity below the glass transition of bulk and ribbon glassy Pd40Cu30Ni10P20 samples differing ,104 -fold in the production quenching rates have been performed. It has been found that heating up into the supercooled liquid region followed by slow cooling leads to a significant structural relaxation-induced viscosity increase upon subsequent testing. This increase, however, is not truly irreversible and the viscosity can be fully recovered (= decreased) by fast quenching from the supercooled liquid state. The effect is nearly independent of whether ribbon or bulk samples are used despite the fact that those latter are notably denser. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Martin Stutzmann: Editor, Teacher, Scientist and FriendPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2005Manuel Cardona On 2 January 1995 Martin Stutzmann became Editor-in-Chief of physica status solidi, replacing Professor E. Gutsche, who had led the journal through the stormy period involving the fall of the Iron Curtain, the unification of Germany and the change in its Eastern part, where physica status solidi was based, from "socialism as found in the real world" (a German concept) to real world capitalism. In 1995 it was thought that the process had been completed (we should have known better!) and after the retirement of Prof. Gutsche the new owners of physica status solidi (Wiley-VCH) decided that a change in scientific management was desirable to adapt to the new socio-political facts and to insure the scientific continuity of the journal. Martin had moved in 1993 from my department at the Max-Planck-Institute to Munich where he soon displayed a tremendous amount of science man- agement ability during the build-up of the Walter Schottky Institute. The search for a successor as Edi- tor-in-Chief was not easy: the job was not very glamorous after the upheavals which had taken place in the editorial world following the political changes. Somebody in the Editorial Boards must have suggested Martin Stutzmann. I am sure that there was opposition: one usually looks for a well-established person ready to leave his direct involvement in science and take up a new endeavor of a more administrative nature. Nevertheless, the powers that be soon realized that Martin was an excellent, if somewhat unconventional candidate who had enough energy to remain a topnotch scientist and to lead the journal in the difficult times ahead: he was offered the job. In the negotiations that followed, he insisted in getting the administrative structures that would allow him to improve the battered quality of the journal and to continue his scientific productivity. Today we are happy to see that he succeeded in both endeavors. The journal has since grown in size and considerably improved its quality. Martin Stutzmann's scientific output has continued and today he can be found listed among the 400 most cited physicists worldwide. According to the Institute of Scientific Information (ISI) he has published nearly 400 articles in source journals; they have been cited over 4600 times. His scientific visibility has been partly responsible for the success of the journal under his leadership. When he took over in 1995 the Impact Factors of physica status solidi (a) and (b) were about 0.5. Now they oscillate around 1.0. The journals occupy places 30 (a) and 29 (b) among the 57 condensed matter publications listed in the ISI. Six years ago these places were 34 (a) and 30 (b). The journal is even better placed with respect to the so-called cited half-life which is 8.2 years for pss (a) (place 16 among 57) and 6.7 years for pss (b) (place 20 among 57). Martin, of course, has contributed with his original publications to the success of the journal, having published 36 articles in pss(a) and 32 in pss(b). I would like to some of the editorial decisions implemented under Martin's leadership. They have been largely responsible for the quantitative improvements just described. Martin introduced international standards of peer review, usually involving two anonymous referees: The increase of the rejection rate from ca. 20% to 60% followed. He discontinued the Short Notes, which had become nearly irrelevant, and replaced them, in 1997 by Rapid Research Notes (today Rapid Research Letters) with especially strict reviewing rules and a rather attractive layout. Martin's participation in many international conferences and their organization gave him a handle to acquire the publication of conference proceedings. Organizing committees usually prefer publication in international journals rather than special books because of their guaranteed future availability in libraries and the partaking in the reviewing procedure. The journal became increasingly popular along these lines, a fact which moved Martin to launch in 2002 part (c) of the journal, devoted mainly, but not exclusively, to conference articles. Martin also introduced the publication of Feature Articles, topical issues, and the instrument of the Editor's Choice to highlight articles deemed to be especially interesting. He appointed Regional Editors (6 at this point) which represent the journal in important geographic regions. He also brought the journal online, a must these days. The upheavals that followed the collapse of most of the communist world, the rapid development of science in many emerging nations and the enhanced competitiveness, even in the developed countries, have not ebbed out. Some of them are particular damaging to the reputation of science in a world increasingly skeptical of its values. I am thinking of scientific misconduct and outright fraud, in the form of plagiarism and data fabrication. physica status solidi was also afflicted by this plague: after all, it happened in the best of families. Two of the most notorious offenders of the past decade, J. H. Schön and Y. Park, also visited physica status solidi. In two courageous editorials Martin Stutzmann and Stefan Hildebrandt (Managing Editor of the journal) rapidly exposed these cases of misconduct together with other cases in which there was also good reason to suspect misconduct. Some of the articles involved were rapidly retracted by the authors, others were not. It is reassuring to say that none of them had any impact worth mentioning (1,3 citations, mostly by the authors themselves or in the editorials just mentioned). Only few journal editors dared to convey to the readers a warning that some work of those authors may be faulty even if no air-tight proof was available. However, Martin and Stefan did. We wish that Martin will remain at the helm at least another decade, before he switches to research on the liquid state as practiced in Southern France. [source] Preparation and properties of polyurethane/montmorillonite nanocomposites cured under room temperaturePOLYMER COMPOSITES, Issue 5 2006Hangbin Jiang The polyurethane/C16C18 -MMT (the montmorillonite modified with cetyloctadecyldimethyl ammonium bromide) nanocomposites were synthesized by intercalative polymerization and cured under room temperature. The d -spacing and the dispersion of the C16C18 -MMT in the nanocomposites were measured by X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM). The mechanical and thermal properties of the nanocomposites were measured by Universal Testing System, Electric Anti-fold Instrument, Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). It was found out that introducing C16C18 -montmorillonite (MMT) in the polyurethane (PU) displayed good mechanical properties and thermal stability. Rheology behavior in liquid state showed that the addition of the C16C18 -MMT to PU resulted in low gel time and high viscosity. POLYM. COMPOS. 27:470,474, 2006. © 2006 Society of Plastics Engineers. [source] High-temperature mass spectrometric study of the vaporization processes of V2O3 and vanadium-containing slagsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2010H. Wang A Knudsen effusion mass spectrometric method was used to study the vaporization processes and thermodynamic properties of pure V2O3 and 14 samples of vanadium-containing slags in the CaO-MgO-Al2O3 -SiO2 system in the temperature range 1875,2625,K. The system was calibrated using gold in the liquid state as the standard. Vaporization was carried out from double tungsten effusion cells. First it was shown that, in vapor over V2O3 and the vanadium-containing slags in the temperature range 1875,2100,K, the following vapor species were present: VO2, VO, O, WO3 and WO2, with the latter two species being formed as a result of interaction with the tungsten crucibles. The temperature dependencies of the partial pressures of these vapor species were obtained over V2O3 and the slags. The ion current comparison method was used for the determination of the V2O3 activities in slags as a function of temperature with solid V2O3 as a reference state. The V2O3 activity coefficients in the slags under investigation indicated positive deviations from ideality at 1900,K and a tendency to ideal behavior at 2100,K. It was shown that the V2O3 activity as a function of the slag basicity decreased at 1900,K and 2000,K and was practically constant in the slag melts at 2100,K. The results are expected to be valuable in the optimization of slag composition in high-alloy steelmaking processes as well as for their environmental implications. Copyright © 2010 John Wiley & Sons, Ltd. [source] Viscous behaviour of quaternary fluid solutions at 298.15,KTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009R. K. Shukla Abstract Assuming a quaternary fluid solution to be made up of six binaries, a statistical approach of Flory has been extended to develop the expression for dynamic viscosity of multicomponent system using the concept of absolute rate and free volume approaches of liquid state. A reasonable agreement has been achieved between theory and the experiment for n -hexadecane,+,carbon tetrachloride,+,benzene,+,n -hexane quaternary system at 298.15 over a wide range of composition. An attempt has also been made to explain the nature of the molecular interactions, involved in the light of excess thermodynamic functions whose sign and magnitude depend upon the chain length and size of the component liquids. En supposant une solution de fluide quaternaire composée de six binaires, on a généralisé l'approche statistique de Flory dans le but d'établir l,expression pour la viscosité dynamique du système multicomposant à l,aide du concept de taux absolu et de l,approche des volumes libres de l,état liquide. Un accord raisonnable a été trouvé entre la théorie et l,expérience pour le système quaternaire n-hexadécane,+,tétrachlorure de carbone,+,benzène,+,n-hexane à 298,15 pour une vaste gamme de composition. On a également tenté d'expliquer la nature des interactions moléculaires, intervenant à la lumière des fonctions thermodynamiques d'excès dont le signe et la grandeur dépendent de la longueur de chaîne et de la quantité des composants liquides. [source] Synthesis, Structure, and Physico-optical Properties of Manganate(II)-Based Ionic LiquidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2010Slawomir Pitula Dr. Abstract Several ionic liquids (ILs) based on complex manganate(II) anions with chloro, bromo, and bis(trifluoromethanesulfonyl)amido (Tf2N) ligands have been synthesized. As counterions, n- alkyl-methylimidazolium (Cnmim) cations of different chain length (alkyl=ethyl (C2), propyl (C3), butyl (C4), hexyl (C6)) were chosen. Except for the 1-hexyl-3-methylimidazolium ILs, all of the prepared compounds could be obtained in a crystalline state at room temperature. However, each of the compounds displayed a strong tendency to form a supercooled liquid. Generally, solidification via a glass transition took place below ,40,°C. Consequently, all of these compounds can be regarded as ionic liquids. Depending on the local coordination environment of Mn2+, green (tetrahedrally coordinated Mn2+) or red (octahedrally coordinated Mn2+) luminescence emission from the 4T(G) level is observed.1 The local coordination of the luminescent Mn2+ centre has been unequivocally established by UV/Vis as well as Raman and IR vibrational spectroscopies. Emission decay times measured at room temperature in the solid state (crystalline or powder) were generally a few ms, although, depending on the ligand, values of up to 25,ms were obtained. For the bromo compounds, the luminescence decay times proved to be almost independent of the physical state and the temperature. However, for the chloro- and bis(trifluoromethanesulfonyl)amido ILs, the emission decay times were found to be dependent on the temperature even in the solid state, indicating that the measured values are strongly influenced by nuclear motion and the vibration of the atoms. In the liquid state, the luminescence of tetrahedrally coordinated Mn2+ could only be observed when the tetrachloromanganate ILs were diluted with the respective halide ILs. However, for [C3mim][Mn(Tf2N)3], in which Mn2+ is in an octahedral coordination environment, a weak red emission from the pure compound was found even in the liquid state at elevated temperatures. [source] Geminal Ionic Liquids: A Combined Approach to Investigate Their Three-Dimensional OrganisationCHEMISTRY - A EUROPEAN JOURNAL, Issue 47 2009Francesca D'Anna Dr. Abstract Different investigations, such as 1D and 2D NMR spectroscopy, resonance light scattering spectroscopy and molecular dynamics simulations, have been jointly used to achieve a deeper understanding of the degree of structural order in two geminal ionic liquids. In particular, 3,3,-di- n -butyl-1,1,-(1,3-phenylenedimethylene)diimidazolium and 3,3,-di- n -butyl-1,1,-(1,4-phenylenedimethylene)diimidazolium bis[bis(trifluoromethanesulfonyl)imide] have been studied. These geminal ionic liquids were chosen because of the presence of both a rigid phenylenedimethylene link between two imidazolium rings, which should give a high degree of order to the solvent system, and the different shapes of the two cations of the isomers, which could induce different properties and packing in the liquid state. Data collected here show that the two geminal ionic liquids are characterised by a different degree of structural order that induces, for example, a different sensitivity of the two solvent systems to temperature changes or to the presence of a co-solvent such as methanol. [source] Probing the Local Structure of Pure Ionic Liquid Salts with Solid- and Liquid-State NMR,CHEMPHYSCHEM, Issue 1 2010Peter G. Gordon Abstract Room-temperature ionic liquids (RTILs) are gaining increasing interest and are considered part of the green chemistry paradigm due to their negligible vapour pressure and ease of recycling. Evidence of liquid-state order, observed by IR and Raman spectroscopy, diffraction studies, and simulated by ab initio methods, has been reported in the literature. Here, quadrupolar nuclei are used as NMR probes to extract information about the solid and possible residual order in the liquid state of RTILs. To this end, the anisotropic nature and field dependence of quadrupolar and chemical shift interactions are exploited. Relaxation time measurements and a search for residual second-order quadrupolar coupling were employed to investigate the molecular motions present in the liquid state and infer what kind of order is present. The results obtained indicate that on a timescale of ,10,8 sec or longer, RTILs behave as isotropic liquids without residual order. [source] Aminosilicone Solvents for CO2 CaptureCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 8 2010Robert Abstract This work describes the first report of the use of an aminosilicone solvent mix for the capture of CO2. To maintain a liquid state, a hydroxyether co-solvent was employed which allowed enhanced physisorption of CO2 in the solvent mixture. Regeneration of the capture solvent system was demonstrated over 6 cycles and absorption isotherms indicate a 25,50,% increase in dynamic CO2 capacity over 30,% MEA. In addition, proof of concept for continuous CO2 absorption was verified. Additionally, modeling to predict heats of reaction of aminosilicone solvents with CO2 was in good agreement with experimental results. [source] A Novel Catalyst for Isobutene Oligomerization to High Quality GasolineCHINESE JOURNAL OF CHEMISTRY, Issue 6 2003Zhou Peng Abstract Dimerization of isobutene in liquid state to form high-octane value gasoline components was investigated over a homemade novel ion exchange resin, SPPESK, which shows high activity and selectivity in isobutene dimerization under mild conditions. [source] | |||||||||||||||||||