Kr Solutions Research Articles

Phase states and the mechanism of crystallization of condensed Ar−Kr mixtures

The structure characteristics of Ar−Kr mixtures deposited under special conditions have been investigated in the whole interval of concentrations applying the transmission electron diffraction technique (THEED). The samples were prepared in situ by condensing a gas mixture preliminary cooled down to the sub-liquid-nitrogen level onto substrates at T = 6 K and 20 K. The experimental results show that the structure and morphology of the Ar−Kr condensates are dependent on the nucleation dynamics prevailing in the course of the sample formation. It is shown that cooling a gas mixture is favorable to the clusterization of solute atoms in the gas flow. The krypton small clusters can serve as condensation clusters. The phase boundaries of the condensates have been determined. Regular Ar−Kr solutions are formed when the contents of one of the components are low (0−10 mol % Ar), (0−5 mol % Kr). The diffraction patterns of the condensates with prevailing Kr contents corresponded to a mixture of Kr-enriched fcc solutions and a dispersed phase of argon. The excess Kr contents are due to the specific morphology of the solutions dictated by condensation conditions. The Ar-based samples contained a mixture of two crystalline phases (an fcc solution and the hcp phase of nearly pure argon) and a glass phase of nearly pure krypton. In the concentration range 58−78 mol % Ar the new morphological form of the Ar−Kr condensates resembles the gel. The phase state diagram of the Ar−Kr condensates has been obtained.

Dapsone uptake and release from plasma polypyrrole for drug administration

A study on dapsone uptake and release model in plasma polypyrrole for drug administration in the central nervous system is presented in this work. The polymer was treated by lyophilization to induce pores on the surface that housed the drug. After that, the polymer was immersed in dapsone–ethanol solutions at different concentrations to introduce the drug into the pores, which once filled the pores, covered the polymer particles. The release of dapsone was tested in water and Krebs–Ringer solutions measured by UV–Vis spectroscopy considering surrounding static and dynamic fluids. The release in both models increased with the contact time in the fluids following linear tendencies. In all cases, the dissolution of the outer dapsone layer of the polymer particles occurred in the first 5 min, which was approximately 10 % of the total dapsone loaded. Dapsone was released at a higher rate in KR solutions than in water, which suggests that the ions of the KR salts help in this process. Morphology and chemical structures are studied before and after adding the drug to the polymer.

Synthesis and superficial characterization of plasma polyfuran thin films

This work presents a study about the synthesis of polyfuran films by plasma and their structural, morphological, electrical and hydrophilic characteristics. The syntheses were carried out at low pressure with resistive electrical glow discharges. The films have thickness in the 7–61 μm interval with a linear tendency as a function of the power of synthesis. The functional groups of the monomer, –C=C– and C–O, and other as C=O produced during the polymerization, were found in the polymers probably as dehydrogenation of =C–H groups in the monomer. The films have contact angles between 52° and 92° for distilled water, but with the addition of salts in KR solutions, the angles slightly increased reducing the hydrophilicity of the system. The conductivity of polyfuran films was calculated in the range of 10−9–10−11 S/m with two trends, one with high electronic activation energy at low temperature, and another with low activation energy at high temperature. The electronic activation energy in the first trend varied between 1.01 and 1.9 eV and in the second trend between 0.26 and 0.08 eV.

Solvation of fluoroform and fluoroform–dimethylether dimer in liquid krypton: A theoretical cryospectroscopic study

A hybrid, sequential statistical physics-quantum mechanical electronic-quantum mechanical nuclei approach has been applied to study the C-H stretching frequencies of bare fluoroform dissolved in liquid krypton under cryogenic conditions (at ~130 K), as well as upon blue shifting hydrogen bonding interactions with dimethylether in the same solvent. The structure of the liquid at 130 K was generated by Monte Carlo simulations of cryogenic Kr solutions containing either fluoroform or fluoroform and dimethylether molecules. Statistically uncorrelated configurations were appropriately chosen from the equilibrated MC runs and supermolecular clusters containing solute and solvent molecules (either standalone or embedded in the "bulk" part of the solvent treated as a polarizable continuum) were subjected to quantum mechanical electronic (QMel) and subsequent quantum mechanical nuclei (QMnuc) calculations. QMel calculations were implemented to generate the in-liquid 1D intramolecular C-H stretching vibrational potential of the fluoroform moiety and subsequently in the QMnuc phase the corresponding anharmonic C-H stretching frequency was computed by diagonalization techniques. Finally, the constructed vibrational density of states histograms were compared to the experimental Raman bands. The calculated anharmonic vibrational frequency shifts of the fluoroform C-H stretching mode upon interaction with dimethylether in liquid Kr are in very good agreement with the experimental data (20.3 at MP2 level vs. 16.6 cm(-1) experimentally). Most of this relatively large frequency blue shift is governed by configurations characterized by a direct C-H···O contact between monomers. The second population detected during MC simulations, characterized by reversed orientation of the monomers, has a minor contribution to the spectral appearance. The experimentally observed trend in the corresponding bandwidths is also correctly reproduced by our theoretical approach. Solvation of the fluoroform monomer, according to experiment, results in small C-H stretching frequency red shift (~-2 cm(-1)), while our approach predicts a blue shift of about 10 cm(-1). By a detailed analysis of the anharmonic C-H stretching frequency dependence on the position of the nearest solvent krypton atom and also by analyzing the vibrational Stark effect induced by the local fluctuating field component parallel to the C-H axis, we have derived several conclusions related to these observations. The frequency vs. C···Kr distance dependence shows appreciable fluctuations and even changes in sign at R values close to the maximum of the C···Kr radial distribution function, so that most of the first-shell Kr atoms are located at positions at which the CH frequency shifts acquire either small negative or small positive values. It so happens, therefore, that even the actual sign of the frequency shift is strongly dependent on the correct description of the first solvation shell around CF3H by the Monte Carlo method, much more than the other in-liquid properties calculated by similar approaches.

A Simulation Study of the Fundamental Vibrational Shifts of HCl Diluted in Ar, Kr, and Xe: Anharmonic Corrections Effects

We have calculated the vibrational solvent shifts of the fundamental bands of HCl diluted in Ar, Kr, and Xe solutions at different thermodynamic conditions by means of the molecular dynamics technique and a model for the isotropic part of the interaction depending on the vibration. The theoretical vibrational shifts, which were compared with the available experimental data, have been determined by considering both, the usual linear Buckingham terms and the nonlinear anharmonic corrections, and the latter omitted in a previous work for the HCl in Ar and Kr. We have found that the Buckingham contributions dominate the solvent shifts of the fundamental bands of HCl in Ar, Kr, and Xe, although the anharmonic shifts’ present significant greater values than those obtained previously for N2 diluted in liquid Ar and pure liquid N2, both at normal conditions. We have analyzed the solvent shifts influence of the linear and quadratic (in the vibrational coordinate) oscillator-bath interaction terms and also the Dunham intramolecular potential effects on the anharmonic contributions.

Differential effect of resuscitation on Toll-like receptors in a model of hemorrhagic shock without a septic challenge

It has been shown that the inflammatory response and cellular damage after hemorrhagic shock are influenced by resuscitation strategies. Toll-like receptors (TLRs) play an important role in signal transduction in inflammatory conditions. However, alterations in TLR expression following hemorrhagic shock and resuscitation have not been well documented. This study was conducted to measure the impact of different resuscitation strategies on TLR expression and downstream signaling in key organs. Sprague Dawley rats (n=38) were subjected to a severe volume-controlled hemorrhage protocol. After 75 min of shock, they were resuscitated over 45 min as follows: (1) lactated Ringer's (LR, 81 ml/kg), (2) ketone Ringer's (KR, 81 ml/kg), (3) 7.5% hypertonic saline (HTS, 9.7 ml/kg), (4) 6% hetastarch (HEX, 27 ml/kg), (5) pyruvate Ringer's (PR, 81 ml/kg). Sham hemorrhage (NH) and no resuscitation (NR) groups served as controls. The KR and PR solutions were identical to LR except for equimolar substitution of racemic lactate with beta hydroxybutyrate and sodium pyruvate, respectively. At the end of resuscitation, the expression of TLRs (types 1-10), and cytokines (IL-10, IL-1beta and TNF-alpha) were measured in the lung and spleen using RT-PCR. Levels of phosphorylated and total IkB-alpha and NF-kappaB were detected by Western blotting. The systemic and lung protein levels of TNF-alpha were measured using ELISA and immunohistochemistry. Expression of TLRs in the lung was affected more than in the spleen by hemorrhagic shock and resuscitation. In the lung, hemorrhage increased TLR-2, -3 and -6 (but not TLR-4) mRNA expression, with an up-regulation of the ratio of phosphor-NF-kappaBp65 and total NF-kappaBp65, NF-kappaBp65 activation, and enhanced systemic and tissue TNF-alpha protein levels. Post-resuscitation, TLR mRNA profile and subsequent downstream proteins in the lung and spleen were affected by the choice of resuscitation strategy. Hemorrhagic shock activates TLR signaling in lung, but not the spleen, probably through an up-regulation of TLR gene expression, and activation of NF-kappaB pathway. Resuscitation modulates this response in a fluid- and tissue-specific fashion.

Heat capacity of solid solutions of deuteromethane in krypton. Nuclear spin conversion in CD4 molecules

A study is made of the heat capacity of the binary solid solutions (CD4)0.01Kr0.99 (in the temperature interval ΔT=0.9–7 K) and (CD4)0.05Kr0.95 (ΔT=0.7–20 K) and of the ternary solid solutions (CD4)0.01Kr0.988(O2)0.002 (ΔT=0.7–11 K) and (CD4)0.05Kr0.948(O2)0.002 (ΔT=0.8–4 K). The contribution of the rotational subsystem to the heat capacity of the solutions is separated out. The influence of temperature, oxygen impurities, and the interaction between the deuteromethane molecules on the effective conversion rate is studied. The energy differences between the lowest-lying levels of the nuclear spin species A and T of deuteromethane is determined, and the effective characteristic conversion times are found. Rapid conversion of isolated CD4 molecules is observed in CD4–Kr solutions. It is shown that in the CD4–Kr solutions, as in CH4–Kr solutions, a hybrid mechanism of conversion is dominant at low temperatures (T<1.4 K), and the “bottleneck” governing the conversion rate is the intermolecular effective octupole–octupole interaction and the related probability of transfer of the conversion energy to phonons.

Infrared studies of acetylene dissolved in liquefied Ar, Kr, N 2, CO, and CO 2

FTIR spectra of acetylene have been studied in liquefied Ar, Kr, N 2, CO and CO 2 in the range ∼1000–9000 cm −1. Width, position and absolute integral intensity of a set of fundamental and combination bands were determined. In the case of ν 3 band an effect of vibrational resonance interaction of Fermi-type has been taken into account and the position of non-perturbed ν 3 0 and ( ν 2+ ν 4+ ν 5) 0 bands were evaluated in the solutions studied. Liquid to crystal state phase transition experiments, performed in Kr solutions, show reversible growth of self-associates when going to lower temperatures of C 2H 2 doped solid Kr. The ν 3(Σ u +) C–H stretch band exhibits weak side shoulders in the case of CO and CO 2 solvents. New combination bands, attributed to ν 2(C 2H 2)+ ν 3(CO 2), ν 3(C 2H 2)+ ν 3(CO 2) and ν 1(C 2H 2)+ ν 3(CO 2) simultaneous transitions due to vibrational excitation of both the interacting partners have been revealed in the region of ∼4000–6000 cm −1. Detecting the ν 3(C 2H 2)+ ν 3(CO 2) combination band, which is forbidden in the frame of dipole approximation, suggests an appreciable role of mutual polarization due to dipole–quadrupole polarizability of molecular partners. The observed spectroscopic features are compared with the results of theoretical DFT/B3LYP and ab initio MP2 calculations utilizing the 6-311++G(3df,3pd) basis set, which predict weak heterodimer formation, with linear H–CC–H⋯CO and slipped parallel H– C C– H O– C– O structures being favored.

IR spectra of CH 3F in liquid and solid noble gas solutions

The IR absorption spectra of CH 3F doped Ar, Kr and Xe solutions have been recorded near the melting point. The full widths at half maximum of fundamental bands increase noticeably after crystallization of the Xe and Kr solutions. A slight narrowing of the bands is observed just below the freezing point of the Ar solution. Treated in the framework of the Debye model for the J-diffusion of a symmetric top rotation, the results suggest a weaker perturbation of rotational motion of CH 3F in the ordered Xe and Kr solids at least near the freezing point. At the same time, molecular rotation becomes more hindered when going to solid Ar. The broadening effect has been found to correlate with a hopping increase of the vibrational energy relaxation time, measured by the IR-IR double resonance method.

Vibrational spectra of OC⋯HCl complex in Kr solutions at liquid to solid phase transition

Fundamental and first overtone bands of HCl, CO molecules and OC⋯HCl complex were studied in liquid and solid Kr solution near the phase transition. Triplet to doublet shape transformations were observed for both fundamental ν(HCl) and first overtone 2ν(HCl) bands at liquid to crystal state transition. Self-association processes of HCl in Kr solutions have resulted in the registration of two to several new sharp peaks on the low frequency P branch of the ν(HCl) band, whereas they only gave an additional diffuse absorption on the P branch of the 2ν(HCl) band. Evolution of the ν(CO) and 2ν(CO) bands, observed at temperature lowering of liquid Kr solution, has shown an increased restriction of the rotational motion of CO in an orienting field of the nearest neighbors. Triplet to singlet shape transformation was found for both the CO bands at liquid to crystal state transition. Asymmetry of the central parts of the bands and high frequency shoulder, which are increased at temperature lowering of the solids, suggest the consecutive transformation of orientational motion of CO into libration and growth of vibrational–translational coupling in CO doped low temperature Kr crystal. OC⋯HCl complex formation with a weak intermolecular H-bond were studied by observation of the red shifted νc(HCl) band and of the blue shifted νc(CO) and 2νc(CO) sharp bands in the solid state. Spectral parameters of dimer bands were estimated.

Infrared studies of weak B…HCl (B = HCl, CO, Xe, N 2) complex formation in solid Kr solutions

IR spectra of small B…HCl (B = HCl, N 2, Xe, CO) complexes have been studied in solid phase at equilibrium conditions by using the technique of crystal growth from a liquid Kr solution. Triplet to doublet structure evolution of the ν(HCl) fundamental band has been revealed at liquid to crystal state transition of the noble (Xe, Kr) gas solutions. Residual rotational structure observed at wings of the ν(HCl) band and spectral moments analysis suggest that noncomplexed HCl molecules continue to rotate in solid solutions studied. Self-association of HCl molecules has been found in solid Kr, while this process was strongly suppressed in solid Xe. Spectral parameters of the ν c fundamental bands and enthalpy of formation ΔH were estimated for B…HCl complexes in solid Kr. Comparative analysis of the ν c (CO) and ν c (HCl) bands shows that the ν c (HCl) bands is perturbed due to intermolecular H-bonding and the OC…HCl complex does not rotate in solid Kr. Relative changes of the integral intensity A of the fundamental ν c (HCl) and ν c (CO) bands due complex formation have been derived from the temperature dependence of the A value.