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Spectroscopically observing the translational and rotational motion of solute molecules in liquid solutions is typically impeded by their interactions with the solvent, which conceal spectral detail through linewidth broadening. Here we show that unique insights into solute dynamics can be made with perfluorinated solvents, which interact weakly with solutes and provide a simplified liquid environment that helps to bridge the gap in our understanding of gas- and liquid-phase dynamics. Specifically, we show that in such solvents, the translational and rotational cooling of an energetic CN radical can be observed directly using ultrafast transient absorption spectroscopy. We observe that translational-energy dissipation within these liquids can be modelled through a series of classic collisions, whereas classically simulated rotational-energy dissipation is shown to be distinctly faster than experimentally measured. We also observe the onset of rotational hindering from nearby solvent molecules, which arises as the average rotational energy of the solute falls below the effective barrier to rotation induced by the solvent. Spectral broadening generally conceals the signatures of rotational and translational motion in solution-phase spectra. Now, using highly inert perfluorocarbon solvents, spectral broadening has been minimized allowing the translational, rotational and vibrational relaxation dynamics of highly excited CN solute molecules to be observed simultaneously.

A nonlinear initial boundary value problem for the lithium ion concentration, the electric potential and the electrode-electrolyte interface currents is introduced on the microscale. The model enables the resolution of porous electrode microstructures. Different exchange current densities for Butler–Volmer interface conditions are evaluated. The Cahn–Hilliard equation is used to describe the phase transition from solid-solution diffusion to two-phase dynamics. The resulting phase-field model is then discretized on a regular mesh. A first-order finite-volume scheme with an adaptive time integration method is applied. The parameters and their effects in the non-convex Helmholtz energy are investigated and explained. Furthermore, the numerical convergence of the scheme is examined. In order to illustrate the method, the charging process of several single-particles and a complex structure is numerically simulated.

Although important to heterogeneous catalysis, the ability to accurately model reactions of polyatomic molecules with metal surfaces has not kept pace with developments in gas phase dynamics. Partnering the specific reaction parameter (SRP) approach to density functional theory with ab initio molecular dynamics (AIMD) extends our ability to model reactions with metals with quantitative accuracy from only the lightest reactant, H2, to essentially all molecules. This is demonstrated with AIMD calculations on CHD3 + Ni(111) in which the SRP functional is fitted to supersonic beam experiments, and validated by showing that AIMD with the resulting functional reproduces initial-state selected sticking measurements with chemical accuracy (4.2 kJ/mol ≈ 1 kcal/mol). The need for only semilocal exchange makes our scheme computationally tractable for dissociation on transition metals.

Flunitrazepam (FNZ) is a sedative–hypnotic benzodiazepine with important therapeutic usefulness and significant abuse liability. Its capability to induce anterograde amnesia favors FNZ use as a “date-rape drug” administered often at a bar or party (“club drug”) by adding it unknowingly to the drinks of victims who will have limited memory of the assault. On the contrary, on the illicit market, “FNZ preparations” may be fake products that do not contain that substance. FNZ combined with anesthetics, opioids, ethanol, cocaine, and methamphetamine can occur in therapeutic use and in polydrug abuse. The FNZ action mechanism involves its binding to the γ-aminobutyric acid receptor (GABAA-R), an intrinsic membrane protein. Changes in the binding site structure by allosteric binding of another drug or by affecting lipid phase dynamics in a receptor's surroundings can modulate this binding activity. Thus, FNZ–GABAA-R binding may serve to sense FNZ concentration, GABAA-R environment organization, and FNZ interaction with other drugs, including polydrug use or abuse conditions.

Over the past two decades, such scale-bridging approaches have matured to provide a better control of morphology-dependent phenomena in several material classes of importance for natural and engineering science. More recently, such scale-bridging approaches have been extended to system-bridging studies, which emerged based on the question: can the analogy between different condensed-matter systems be taken so far that the investigation of experimentally and theoretically simple-to-handle systems can answer questions of interfacial and phase-dynamics in a general system-independent manner? This article discusses the perspectives of the arising scale- and system-bridging research approaches in condensed matter physics.

We hypothesized that, associated with the state of anaesthesia, characteristic changes exist in both cardio-respiratory and cerebral oscillator parameters and couplings, perhaps varying with depth of anaesthesia. Electrocardiograms (ECGs), respiration and electroencephalograms (EEGs) were recorded from two groups of 10 rats during the entire course of anaesthesia following the administration of a single bolus of ketamine–xylazine (KX group) or pentobarbital (PB group). The phase dynamics approach was then used to extract the instantaneous frequencies of heart beat, respiration and slow δ-waves (within 0.5–3.5 Hz). The amplitudes of δ- and θ-waves were analysed by use of a time–frequency representation of the EEG signal within 0.5–7.5 Hz obtained by wavelet transformation, using the Morlet mother wavelet. For the KX group, where slow δ-waves constituted the dominant spectral component, the Hilbert transform was applied to obtain the instantaneous δ-frequency. The θ-activity was spread over too wide a spectral range for its phase to be meaningfully defined. For both agents, we observed two distinct phases of anaesthesia, with a marked increase in θ-wave activity occurring on passage from a deeper phase of anaesthesia to a shallower one. In other respects, the effects of the two anaesthetics were very different. For KX anaesthesia, the two phases were separated by a marked change in all three instantaneous frequencies: stable, deep, anaesthesia with small frequency variability was followed by a sharp transition to shallow anaesthesia with large frequency variability, lasting until the animal awoke. The transition occurred 16–76 min after injection of the anaesthetic, with simultaneous reduction in the δ-wave amplitude. For PB anaesthesia, the two epochs were separated by the return of a positive response to the pinch test at 53–94 min, following which it took a further period of 45–70 min for the animal to awaken. δ-Waves were not apparent at any stage of PB anaesthesia. We applied non-linear dynamics and information theory to seek evidence of causal relationships between the cardiac, respiratory and slow δ-oscillations. We demonstrate that, for both groups, respiration drives the cardiac oscillator during deep anaesthesia. During shallow KX anaesthesia the direction either reverses, or the cardio-respiratory interaction becomes insignificant; in the deep phase, there is a unidirectional deterministic interaction of respiration with slow δ-oscillations. For PB anaesthesia, the cardio-respiratory interaction weakens during the second phase but, otherwise, there is no observable change in the interactions. We conclude that non-linear dynamics and information theory can be used to identify different stages of anaesthesia and the effects of different anaesthetics.

Lithium and sodium compounds supported by tetradentate amino-bis(phenolato) ligands, [Li2(N2O2(BuBuPip))] (1), [Na2(N2O2(BuBuPip))] (2) (where [N2O2(BuBuPip)] = 2,2'-N,N'-homopiperazinyl-bis(2-methylene-4,6-tert-butylphenol), and [Li2(N2O2(BuMePip))] (3), [Na2(N2O2(BuMePip))] (4) (where [N2O2(BuMePip)] = 2,2'-N,N'-homopiperazinyl-bis(2-methylene-4-methyl-6-tert-butylphenol) were synthesized and characterized by NMR spectroscopy and MALDI-TOF mass spectrometry. Variable temperature NMR experiments were performed to understand solution-phase dynamics. The solid-state structures of 1 and 4 were determined by X-ray diffraction and reveal tetrametallic species. PGSE NMR spectroscopic data suggests that 1 maintains its aggregated structure in CD2Cl2. The complexes exhibit good activity for controlled ring-opening polymerization of rac-lactide (LA) both solvent free and in solution to yield PLA with low dispersities. Stoichiometric reactions suggest that the formation of PLA may proceed by the typical coordination-insertion mechanism. For example, (7)Li NMR experiments show growth of a new resonance when 1 is mixed with 1 equiv. LA and (1)H NMR data suggests formation of a Li-alkoxide species upon reaction of 1 with BnOH.

The 267 nm photodissociation dynamics of p-methylthiophenol (p-MePhSH) and p-methylthioanisole (p-MePhSMe) dissolved in CD3CN have been probed by subpicosecond time-resolved broadband infrared spectroscopy. Prompt (τ < 1 ps) S-H bond fission in p-MePhSH is confirmed by monitoring the time-evolution of the parent (S0) bleach and the transient absorption of the p-MePhS products. Vibrational relaxation of the latter occurs on a ∼8.5 ps time scale, and ∼40% of the total radical population undergoes geminate recombination over a ∼150 ps time scale, yielding (mainly) the p-MePhSH(S0) parent. S-Me bond fission following photoexcitation to the S1 state of p-MePhSMe occurs over a much longer timescale, with a rate that is very dependent on the degree of vibrational excitation within S1. The various findings are compared and contrasted with results from complementary gas-phase photofragmentation studies of both molecules, which are shown to provide a valuable starting point for describing the solution-phase dynamics.

Partial (triangular) decoupling of MIMO systems has been considered in the literature as a way of relaxing the design limitations introduced by diagonal decoupling in non-minimum phase processes. The former strategy allows decoupling a variable of interest without affecting it with non-minimum phase dynamics. However, when right-half plane (RHP) zeros are mainly aligned with this variable, pushing the effect of the RHP zeros to other outputs comes at the cost of great interactions in those variables. This article presents a method to delimit these interactions without degrading significantly the decoupled variable response. To this end, the algorithm shapes the reference signal by means of an auxiliary sliding mode loop.

The end-over-end rotational motion of nematic-phase molecules was examined by an isobaric-isothermal molecular-dynamics simulation for a Gay-Berne mesogenic system. The result was compared with the Meier-Saupe theory and the previous result obtained from a molecular-dynamics simulation for the same Gay-Berne model at constant volume in order to examine the influence of volume fluctuation on nematic-phase dynamics. The results from the simulation at constant pressure were closer to the theoretical value the retardation factor g||, which is the concept used to interpret reduction of the relaxation time for end-over-end rotational molecular motion, throughout the entire range of the second-rank orientational order parameter and the strength parameter of Maier-Saupe form σ than were those values for constant volume. Volume fluctuation is important in evaluating the retardation factor g||. This finding significantly increases our understanding of the role of pressure control in the simulation of slow dynamics in the liquid crystalline phase.

Experimental evidence is provided to show the effect of gas phase dynamics on the onset of thermal convection and on the accompanying patterns in a silicone oil-air convecting bilayer. Very good agreement with three-dimensional calculations for linearized stability is obtained mostly for small and large gas heights. Reasons for this agreement as well as the results at intermediate gas heights are qualitatively explained from the perspective of well-established nonlinear analysis.

The effects of the solvent and finite temperature (entropy) on the Wittig reaction are studied by using density functional theory in combination with molecular dynamics and a continuum solvation model. Standard gas-phase zero-temperature calculations are found to give similar results to previous studies. Gas-phase dynamics simulations allow the free energy profile of the reaction to be calculated through thermodynamic integration. The free energy profile is found to have a significant entropic barrier to the addition step of the reaction where only a small barrier was present in the potential energy curve. The introduction of the solvent dimethyl sulfoxide causes a change in the structure of the intermediate from the oxaphosphetane structure to the dipolar betaine structure. The overall reaction energy is changed only slightly. When the effects of both entropy and the solvent are included a significant entropic barrier to the addition reaction is obtained and the predicted intermediate again has the betaine structure.

This paper presents the results of a series of experimental tests about the absorption of water vapour by an aqueous lithium bromide solution over a bundle of 14 smooth tubes, using an alcohol (2-ethyl-1-hexanol) as surfactant. It follows the same multi-factorial methodology used in a previous article, in order to compare with the experiences without the alcohol. The study reveals that the 2-ethyl-1-hexanol strongly affects the hydrodynamics and the heat and mass transfer as is already known. However, new insight about the absorption process is gained by comparing our experiences with less common theoretical works on falling film stability where some parallelisms are identified. As a result, the main parameters that control this dynamic process seem to be the Marangoni number and also the Reynolds number, as many authors would point out as obvious. But it is much less obvious, that they do interact with each other to create a stability window and to determine the pattern of the flow and therefore the mass transfer rate. Finally in the conclusions a comment on how this could be used in practice is also done and some further research proposed, as for instance, the implication, or not, of the Soret effect in the inter-phase dynamics of the surfactant (2-ethyl-1-hexanol in our case) for aqueous lithium bromide solutions.

We report on DFWM spectroscopy on the asymmetric stretching mode in a-SiOx with x from 0.1 to 1.11. For a-SiO0.1, a 10 K lifetime of 2.8 ps is obtained using laser-induced transient grating spectroscopy. Two-pulse photon echo measurements reveal phase dynamics having a temperature dependent component due to elastic phonon scattering and an excitation dependent component suggesting the presence of non-equilibrium Si-Si modes. At high excitation densities, the DFWM signal is dominated by a quasi-thermal grating whose population decay is extremely long lived (much greater than 1 ns). This effect is enhanced as the oxygen concentration is increased. (C) 2004 Elsevier B.V. All rights reserved.

The activities of lectins and peroxidase and lignin content were studied in the perilesional area of leaves in two tobacco species (Nicotiana tabacumL., cultivar Samsun NN, and N. glutinosa L.) inoculated with tobacco mosaic virus. The development of hypersensitivity response proved to be accompanied by a complex spatial and temporal distribution of lectin activity. The area 5–9 mm away from the lesion center was characterized by the highest activity of loosely bound membrane lectins eluted with 0.05% Triton X-100. In the fraction of tightly bound membrane lectins (eluted with 0.5% detergent), lectin activity decreased during the first two days but increased on day 4 after inoculation. The activity of loosely bound membrane lectins increased in the leaf areas distant from the lesion. Two-phase dynamics in the interlesional area were also observed for lectin activity in the tightly bound membrane fraction (decrease on day 2 days and increase on day 4 after inoculation) and for peroxidase activity (increase on day 2 days and decrease on day 4). The relationship between the dynamics and spatial distribution of lectins in the perilesional area and the possible involvement of these proteins in pathogen-induced changes in photosynthesis are discussed.

OCTA is an integrated multi scale computer simulation platform for polymeric materials design. OCTA consists of four simulation programs and a common graphical user interface. Applicability of the OCTA was investigated to linear homo polymer blend systems such as heterophasic polyolefin-based elastomer blend systems. A morphology simulator SUSHI which utilized a mean field simulation system based on the self consistent field theory, was employed to predict the morphology of bulk materials which have multiphase structure, binary Polypropylene (PP)/Ethylene-Propylene-Rubber (EPR) and ternary PP/EPR/Polyethylene (PE) polymer blend systems. And the elastic modulus was predicted by MUFFIN/Elastica which is a part of multi phase dynamics simulator based on the finite element method, using the morphology of elastomer blend systems calculated by SUSHI. Predicted moduli show very good agreement to literature data of elastomer blend systems. Zooming-simulation scheme, combination of any simulation models with different scale, is a successful method for designing soft materials.

The evaporation mechanism at high temperatures is one of the disputable points of the conventional thermal model of laser ablation connecting heat transfer in the target with gas-phase dynamics. A model of supercritical ablation is proposed where the vapour density is limited by a transparency condition. The model is basically laser–vapour coupling in a thin near-surface layer. The experiments on ablation of Au at 193 and 266 nm, Al at 266 nm, and graphite at 1.06 µm can be described by the proposed model. However, optical breakdown is important in graphite ablation at 193 and 248 nm. When the target surface temperature is less than the critical one (typically at fluences less than or about several J cm−2) the thermal evaporation mechanism works. At higher laser fluences it has been found that a combination of the proposed supercritical ablation mechanism with optical breakdown in the volume of the gas phase is more realistic.

Deuterium fluoride gets born shivering Modern spectroscopic techniques can analyze collisions between gas phase molecules in exquisite detail, highlighting exactly which vibrations and rotations come into play. However, much chemistry of interest takes place in solution, where it's harder to tease out what happens. Dunning et al. applied infrared spectroscopy to study solution-phase formation of deuterium fluoride (DF) from F atoms, a longstanding test bed of gas phase dynamics. The DF product vibrated for a surprisingly long time before dissipating its energy to the surrounding solvent molecules. Science , this issue p. 530

The gas phase dynamics of an inverted, stagnation point flow CVD reactor were studied by both experiment and modeling. The axial centerline temperature profile in the reactor was measured by analysis of the rotational Raman spectra from the carrier gas ( No r H) as a function of the inlet flow velocity and the reactor aspect ratio.It was found that a larger temperature gradient 22 normal to the susceptor surface was obtained with higher gas flow velocity, larger aspect ratio, and the use of a N carrier gas. 2 A two-dimensional axisymmetric model with detailed heat transfer descriptions predicted the experimental data well.The validated model clearly demonstrates that recirculation flows are less likely in inverted reactor geometry. 2002 Elsevier Science B.V. All rights reserved.

Solution processed organic–inorganic metal halide perovskite and its derivatives are promising in the development of efficient thin film photovoltaic devices. In the context of increasing the efficiency and sustainability of perovskite solar cells (PSC) devices, we have attempted to experimentally develop phase diagram for solution processed methyl ammonium lead iodide (CH3NH3PbI3 (MAPbI3)) perovskite. The phase diagram emphasized the role of processing parameters (precursor composition and crystallization temperature) on the crystallographic functionality and optical band gap of perovskite. The phase dynamics of low dimensional perovskite, which has emerged as a potential candidate for absorber layer in perovskite solar cells (PSC) with higher stability in ambient conditions is also discussed. We observed that crystallization via non-equilibrium annealing introduced lattice strain in perovskite which affected the crystallographic properties of perovskite. A highly crystalline perovskite, with large grain size was obtained by optimizing the crystallization parameters and precursor composition together with nucleation of perovskite crystal and its growth dynamics.

Bimolecular reactions in the gas phase exhibit rich and varied dynamical behaviour, but whether a profound knowledge of the mechanisms of isolated reactive collisions can usefully inform our understanding of reactions in liquid solutions remains an open question. The fluctuating environment in a liquid may significantly alter the motions of the reacting particles and the flow of energy into the reaction products after a transition state has been crossed. Recent experimental and computational studies of exothermic reactions of CN radicals with organic molecules indicate that many features of the gas-phase dynamics are retained in solution. However, observed differences may also provide information on the ways in which a solvent modifies fundamental chemical mechanisms. This perspective examines progress in the use of time-resolved infra-red spectroscopy to study reaction dynamics in liquids, discusses how existing theories can guide the interpretation of experimental data, and suggests future challenges for this field of research. (C) 2014 AIP Publishing LLC.

Experiments on the field and frequency dependence of ac susceptibility (acs) for an amorphous Fe 80 Mn 10 Zr 10 alloy in the temperature range from 12 to 300 K are used to explore magnetic nature. There is a well-resolved frequency dependent maximum in the imaginary component of the acs at low temperature, which is the real significance of the reentrant spin-glass phase dynamics. The dynamic scaling analysis of the low field acs data indicates the presence of spin-glass transition T SG =40 K with a critical exponent Ψ =6.5 which seems to be a mixed state rather than a pure spin-glass state. The existence of mixed magnetic state could be understood based on exchange frustration model.

We develop a numerically exact approach to the quantum-phase and information-entropy dynamics of a molecular aggregate interacting with quantized fields. It is well known that a peculiar quantum nature, i.e., collapses and revivals, is observed in monomer and noninteracting aggregate models. In this article, we investigate the intermolecular interaction effects on the collapse-revival behavior using several dimer models (composed of two-state monomers with different intermolecular distances) interacting with a single-mode coherent photon field. The intermolecular interaction is taken into account by using the dipole-dipole interaction. Also, one- and two-exciton dimer models are considered in order to elucidate the exciton contributions to collapse-revival behavior. This quantum behavior is analyzed from the viewpoint of the dynamics of Pegg-Barnett photon-phase and information-entropy of dimers, which closely relate to the time evolution of quantum coherency between the ground and the excited dimer states and the degree of the entanglement between dimer and photon, respectively. It is found that the intermolecular interaction and the two-exciton generation provide remarkable changes in the collapse-revival behavior through their significant influence on the quantum-phase dynamics and the photon-dimer entanglement. From the dimer entropy dynamics, intermediate intermolecular interaction is found to cause the momentary decrease in the photon-dimer correlation in the early time region. This feature leads to the enhancement of off-diagonal density (quantum coherency) between two dimers. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 530-545, 2001

Experiments have been performed on the interaction physics of laser light with polystyrene and agar–agar foams having average densities higher than critical. The experiments have been performed at the ABC facility of the Associazione EURATOM-ENEA sulla Fusione, in Frascati. The main addressed topics have been energy coupling (balance), diffusion of energy into the target, plasma and dense phase dynamics, and harmonics generation. The laser light (λ = 1.054 μm) was focused by a F/1 lens to produce on the target surface about 1.6 × 1014 W/cm2 (≈1015 W/cm2 in the waist, set about 100 μm inside the target). Experiments have shown efficient energy coupling (>80%) to be attributed to cavity formation in the low density foam (efficient light absorption) and good mechanical coupling of the plasma trapped in the cavity to the dense phase (ablation pressure work). Heat diffusion possibly plays a transitory role in the initial stages of the interaction (300–500 ps). Time integrated harmonics measurements revealed a blue-shifted 2ω and a red-shifted 5/2ω.

The transport and structural phase dynamics exhibited by multilayer assemblies comprised of cyclic and linear alkanes are analyzed with reflection absorption infrared (RAIR) and temperature-programmed desorption spectroscopies. Infrared spectroscopy reveals that methyl group substitutions have a significant effect on the nature of the mode softening seen in the C-H stretching region for surface-bound cyclohexanes. The magnitude of the red-shifts seen increases with the degree of methyl substitution. The energetics of the surface binding do not correlate in a simple way with the magnitude of red-shifts seen in the RAIR spectra, however. We find instead that the strengths of the surface interactions are more directly correlated with both the size and shape of the molecule (with the latter presumably reflecting its ability to form a densely packed structure). We also find that the diffusion of molecules in a mixed hydrocarbon multilayer assembly is weakly activated, with substantial interlayer mixing being seen at temperatures significantly below the threshold for the desorption of the multilayer. The mixing, while driven by mass action, shows a pronounced bias for the surface binding of n-alkanes over cycloalkanes of similar molecular weight (e.g., n-octane is more strongly bound on Pt(111) than is cis-1,3-dimethylcyclohexane). The data strongly suggest that attractive lateral interactions in the adsorbed layers lead to the biases seen in this surface-induced segregation. Thermal desorption spectra confirm this sensitivity and interestingly show multiple monolayer desorption features for cyclic alkane adsorbates when mixed in a monolayer assembly with an appropriate linear n-alkane. We suggest that the attractive lateral interactions in the monolayer lead to the formation of island domains and that the desorption kinetics appear to sensitively reflect this underlying rate/structure sensitivity.

The etching of silicon in remote microwave discharges fed with NF3/O2 has been investigated. In situ ellipsometry and x-ray photoelectron spectroscopy (XPS) were used to monitor surface effects, while mass spectrometry was used to monitor the gas phase dynamics. Varying the microwave power from 600 to 1400 W has little effect, due to the near complete dissociation of the NF3, even at lower powers. For discharges containing pure NF3, the poly-Si etch rate increases linearly with NF3 flow. When a low proportion of O2 (O2/NF3=0.1) is added to the discharge, the etch rate increases quickly to its maximum of ∼700 nm/min. With further O2 addition, this etch rate decreases below that observed for pure NF3 processing. The fluorine concentration in the processing region decreases for all O2 additions by a dilution effect. For pure NF3 discharges, XPS measurements reveal 1–2 nm thick, highly fluorinated reaction layers with a gradual loss of fluorine content as the NF3 flow is increased. Specimens processed with bo...

We recently reported the first pump−probe measurements on the hydrated electron with sufficient time resolution (∼35 fs) to directly observe the initial processes in the solvation dynamics of this key prototype for condensed-phase dynamics [Silva, C.; Walhout, P. K.; Yokoyama, K.; Barbara, P. F. Phys. Rev. Lett. 1998, 80, 1086]. An unprecedented relaxation process for the hydrated electron was observed that occurs on the 35−80 fs time scale and exhibits a solvent isotope effect (τ(D2O)/τ(H2O) ∼ 1.4). The new process was assigned to inertial/librational motion of the water surrounding the excess electron. The present paper reports a more extensive study of the ∼35 fs resolved dynamics of the hydrated electron in H2O and D2O at more probe wavelengths and as a function of pump-pulse intensity. The results are in agreement with the preliminary report and support the importance of librational water motion in the relaxation dynamics of the hydrated electron. New high excitation pulse intensity measurements reve...

High temperature Mossbauer spectroscopy has been used for studying “in situ” the phase dynamics of the silicon rich part of the binary Fe-Si system. In particular the rate and mechanism of the transformation of the so-called zeta-alpha phase of iron disilicide to the zeta-beta phase is of special interest, since there still remains uncertainty about the stability and the structure of the phase in this system which influence material properties such as compressive strength and disintegration. In the present work the phase transition from the zeta-alpha phase to the zeta-beta phase is followed by a time sequence of Mossbauer spectra recorded every three hours at a fixed temperature around 800 K. The exponential precipitation rate is analysed and the exponent calculated. Samples with differing degree of impurities have been studied and the effect of aluminium impurities on the rate of the transition will be discussed. The Debye temperature of the two phases was determined from series of Mossbauer spectra recorded at temperatures between 300 and 800 K.

Interactions between acoustic waves and the transient combustion response of a double-base homogeneous propellant in a rocket motor have been analyzed numerically. The analysis extends the previous work on gas-phase flame dynamics to include the coupling with condensed-phase processes. Consequently, a more complete description of propellant combustion response to imposed acoustic oscillations can be obtained. Emphasis is placed on the near-surface flame-zone physiochemistry and its coupling with unsteady propellant burning in an oscillatory environment. The formulation treats complete conservation equations and the finite-rate chemical kinetics in both the gas-phase and subsurface regions. The instantaneous propellant burning rate is predicted as part of the solution. Various distinct features of unsteady heat release arising from propellant combustion response in a motor with forced oscillations are studied systematically. As in the pure gas-phase dynamics of the previous case, the dynamic behavior of the luminous flame plays a decisive role in determining the motor stability characteristics. However, the propellant combustion response may qualitatively modify the temporal evolution of heat-release distribution in the luminous flame and as a result exerts a significant influence on the global stability behavior. The primary flame structure adjacent to the propellant surface is usually little affected by flow oscillation. This may be attributed to the large thermal inertial of the condensed phase, which tends to restrain the temperature variation in the near-surface zone in the present study of laminar flows. The situation with a turbulent flow may be drastically different, as turbulence may penetrate directly into the, primary flame and substantially change the local flame dynamics and transport phenomena.

Thermo-mechanical deformation of Neodymium doped glass slabs during high-power laser shots strongly affects the beam wave-front. The thermally distorted phase profile is corrected with an adaptative mirror on the French Ligne d'Integration Laser (LIL), the 8-beam prototype of the Laser Megajoule (LMJ). Nitrogen cooling of the flash lamps reduces the delay needed to reach thermal equilibrium between two shots by optimizing the slab relaxation back to their original shape. The wave-front is measured before, during, and after a shot with a Shack-Hartmann wave-front sensor. To predict and control the phase profile during cooling, phase dynamics is computed from the thermo-mechanical properties of the slab. Numerical results and measurements are in good qualitative and quantitative agreement.

In the present work, examples of protein and peptide complexes conformational dynamics, from the solvent state distribution to the gas-phase “de-solvated” state distribution, are characterized for traditionally considered “unstructured” complexes. Conformational motifs and isomerization/conformational dynamics are identified and isomerization kinetics in the ms to few seconds timescale are measured for single molecules using a trapped ion mobility spectrometer - mass spectrometer (TIMS-MS). Theoretical calculations are used to simulate the experimental “TIMS box” single molecule -neutral bath gas phase dynamics and candidate structures are proposed for each conformational state. It is found that, side chain and backbone structural changes are the main motifs governing the conformational inter-conversion processes in the ms-s time scale. Examples will be shown for the case of folded/unfolded protein complexes and DNA-binding proteins.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Here, we introduce a mass spectrometry-based analytical method and relevant technical details for dynamic cell respiration and CO2 labeling analysis. Such measurements can be utilized as additional information and constraints for model-based (13)C metabolic flux analysis. Dissolved dynamics of oxygen consumption and CO2 mass isotopomer evolution from (13)C-labeled tracer substrates through different cellular processes can be precisely measured on-line using a miniaturized reactor system equipped with a membrane-inlet mass spectrometer. The corresponding specific rates of physiologically relevant gases and CO2 mass isotopomers can be quantified within a short-term range based on the liquid-phase dynamics of dissolved fermentation gases.

We previously identified the heterogeneous ribonucleoprotein SAF-A/hnRNP U as a substrate for DNA-PK, a protein kinase involved in DNA damage response (DDR). Using laser micro-irradiation in human cells, we report here that SAF-A exhibits a two-phase dynamics at sites of DNA damage, with a rapid and transient recruitment followed by a prolonged exclusion. SAF-A recruitment corresponds to its binding to Poly(ADP-ribose) while its exclusion is dependent on the activity of ATM, ATR and DNA-PK and reflects the dissociation from chromatin of SAF-A associated with ongoing transcription. Having established that SAF-A RNA-binding domain recapitulates SAF-A dynamics, we show that this domain is part of a complex comprising several mRNA biogenesis proteins of which at least two, FUS/TLS and TAFII68/TAF15, exhibit similar biphasic dynamics at sites of damage. Using an original reporter for live imaging of DNA:RNA hybrids (R-loops), we show a transient transcription-dependent accumulation of R-loops at sites of DNA damage that is prolonged upon inhibition of RNA biogenesis factors exclusion. We propose that a new component of the DDR is an active anti-R-loop mechanism operating at damaged transcribed sites which includes the exclusion of mRNA biogenesis factors such as SAF-A, FUS and TAF15.

A newly developed frequency and time resolved coherent anti-Stokes Raman scattering (CARS) technique is used to study properties of the A1g ring breathing mode of benzene in a dilution series of liquid mixtures with n-hexane. Recent advances in the interferometric use of incoherent light in CARS measurements (I(2)CARS) provide excellent precision in the recovered dephasing rate constants, vibrational frequencies, and the ratios of the resonant to non-resonant contributions to the signal. Using this technique we observe a more than two-fold decrease in the dephasing rate constant of the vibration, accompanied by a 0.54 cm−1 increase in the vibrational frequency in the limit of infinite dilution of benzene in n-hexane. These changes in the vibrational spectrum are discussed in terms of the condensed phase dynamics that are responsible. It is also seen how the non-resonant contributions to the signal manifest themselves quantitatively in these frequency and time resolved I(2)CARS measurements.

Molecular ions undergoing ultrafast conformational changes on the same time scale of water motions are of significant importance in condensed phase dynamics. However, the characterization of systems with fast molecular motions has proven to be both experimentally and theoretically challenging. Here, we report the vibrational dynamics of the non-degenerate (C12,C13)-oxalate anion, an ultrafast rotor, in aqueous solution. The infrared absorption spectrum of the (C12,C13)-oxalate ion in solution reveals two vibrational transitions separated by approximately 40 cm(-1) in the 1500-1600 cm(-1) region. These two transitions are assigned to vibrational modes mainly localized in each of the carboxylate asymmetric stretch of the ion. Two-dimensional infrared spectra reveal the presence and growth of cross-peaks between these two transitions which are indicative of coupling and population transfer, respectively. A characteristic time of sub-picosecond cross-peaks growth is observed. Ultrafast pump-probe anisotropy studies reveal essentially the same characteristic time for the dipole reorientation. All the experimental data are well modeled in terms of a system undergoing ultrafast population transfer between localized states. Comparison of the experimental observations with simulations reveal a reasonable agreement, although a mechanism including only the fluctuations of the coupling caused by the changes in the dihedral angle of the rotor, is not sufficient to explain the observed ultrafast population transfer.

The solubility of Cd in contaminated paddy soils controls Cd uptake by rice which is an important food safety issue. We investigated the solution and solid phase dynamics of Cd in a paddy soil spiked with ~20 mg kg 1 Cd during 40 days of soil reduction followed by 28 days of soil reoxidation as a function of the amounts of sulfate available for microbial reduction and of Cu that competes with Cd for precipitation with biogenic sulfide. At an excess of sulfate over (Cd + Cu) dissolved Cd decreased during sulfate reduction and Cd was transformed into a poorly soluble phase identified as Cd sulfide using Cd K edge X ray absorption spectroscopy (XAS). The extent of Cd sulfide precipitation decreased with decreasing sulfate and increasing Cu contents even if sulfate exceeded Cd. When both Cu and Cd exceeded sulfate dissolved and mobilizable Cd remained elevated after 40 days of soil reduction. During soil reoxidation Cd sulfide was readily transformed back into more soluble species. Our data suggest that Cd sulfide formation in flooded paddy soil may be limited when the amounts of Cd and other chalcophile metals significantly exceed reducible sulfate Therefore in multimetal contaminated paddy soils with low sulfate contents Cd may remain labile during soil flooding which enhances the risk for Cd transfer into rice. © 2013 American Chemical Society.

Silicon (Si) nanoparticles were coated inflight with silver (Ag) atoms using a novel method to prepare multicomponent heterostructured metal-semiconductor nanoparticles. Molecular dynamics (MD) computer simulations were employed, supported by high-resolution bright field (BF) transmission electron microscopy (HRTEM) and aberration-corrected scanning transmission electron microscopy (STEM) with a resolution ≤0.1 nm in high angle annular dark field (HAADF) mode. These studies revealed that the alloying behavior and phase dynamics during the coating process are more complex than when attaching hetero-atoms to preformed nanoparticles. According to the MD simulations, Ag atoms condense, nucleate and diffuse into the liquid Si nanoparticles in a process that we term “inoculation”, and a phase transition begins. Subsequent solidification involves an intermediate alloying stage that enabled us to control the microstructure and crystallinity of the solidified hybrid heterostructured nanoparticles.

A laboratory-scale atomic layer deposition (ALD) reactor system model is derived for alumina deposition using trimethylaluminum and water as precursors. Model components describing the precursor thermophysical properties, reactor-scale gas-phase dynamics and surface reaction kinetics derived from absolute reaction rate theory are integrated to simulate the complete reactor system. Limit-cycle solutions defining continuous cyclic ALD reactor operation are computed with a fixed point algorithm based on collocation discretization in time, resulting in an unambiguous definition of film growth-per-cycle (gpc). A key finding of this study is that unintended chemical vapor deposition conditions can mask regions of operation that would otherwise correspond to ideal saturating ALD operation. The use of the simulator for assisting in process design decisions is presented.

Ethylene-bridged azobenzene (diazocine) has been shown to have superior photochemical properties. So far, however, experimental and theoretical quantum yields did not match, not even qualitatively. Here, a large-scale QM/MM surface-hopping study of this molecule is presented. For both photo-isomerization directions, surprisingly prominent solvent effects are found and analyzed by detailed comparisons against gas phase dynamics and experimental data. By taking explicit n-hexane solvent into account, the quantum yields change markedly and approach the experimental values, where the same solvent was used.

Path-branching representation (or phase-space averaging and natural branching method (PSANB) as its approximation) of nonadiabatic electron wavepacket dynamics is now known to work well for avoided crossings in many dimensional nonadiabatic transitions [Yonehara, T.; Hanasaki, K.; Takatsuka, K. Chem. Rev. 2012, 112, 499]. In this paper we examine feasibility of the path-branching representation in the theoretical studies of conical intersection (CI). The most characteristic feature of CI is the Herzberg-Longuet-Higgins phase (or the Berry phase) arising from the electronic part of the total wave function, and accordingly quantum phases of both electronic and nuclear dynamics should be taken into account in a balanced manner. We first show the PSANB can well capture the essential feature of the phase dynamics of CI. However, the nuclear phases, the wavelength of which is far shorter than that of the electronic phases, make the computation of nonadiabatic transition extremely oscillatory, resulting in very slow convergence with respect to the number of sampling paths. A similar difficulty quite often takes place in theoretical chemical dynamics. To cope with this situation, we devise a simple and tractable approximation in the application of PSANB resting on the fact that a small number of PSANB paths already reproduce accurate nonadiabatic transition probability.

The role of the solvent in the liquid phase dynamics of unimolecular processes involving small energy barriers is studied by ultrafast laser spectroscopy. Different regions of the interaction potential between the solvent environment and the reactant are characterized by investigating photoisomerization reactions of trans-stilbene and related compounds in liquid n-alkanes and n-alkanols over a wide pressure range. By varying the physical properties of the solvent environment in such a controlled way, aspects of the reactant - solvent interaction which dominate the different density regimes are identified. In particular, the kind of friction acting along the reaction path, the role of solvent-induced changes of the effective potential energy surface for reaction, and the coupling of dielectric solvent shell relaxation and motion along the reaction coordinate are addressed.

Large-amplitude solid phase molecular motion has been detected in the macrocyclic ring of the title crown either via 13C CPMAS NMR. To study the details of the dynamic processes, two selectively deuterated d4 derivatives have been prepared and examined via 2H NMR as a function of temperature. A phase change occurring around 277 K has been verified by differential scanning calorimetry (DSC) and a model for the motional processes has been developed involving equivalent two-site flips of the CD2 groups. The amplitude of the CD2 motions apparently decreases the closer the group is to the aromatic ring. The influence of KNCS complexation on the 13C CPMAS spectrum and on 13C spin lattice relaxation times in solution has been explored. Key words: macrocyclic ethers, solid phase dynamics.

An experimental study of the solid phase dynamics in a three-phase fluidized bed reactor using heavy and light particles is carried out. A radioactive particle tracking technique is employed to obtain extended time series of the tracer path. The tracer has the same properties as the rest of the particles in the bed. A resealed range analysis is applied to time series of the fluctuating velocities to investigate the features of solid phase turbulence. It is found that turbulence is anisotropic. In the axial direction, the correlations between the fluctuating velocities are persistent in time, indicating a superdispersive axial dispersion of the solids. Hence a constant axial dispersion coefficient, which is traditionally used in these reactors to represent the solid phase turbulence, only constitutes a lumped parameter hardly extrapolable to different operating conditions, different systems, and different geometries. The tracer path is also analyzed according to the theory of deterministic chaos. It is found that the solids motion is chaotic. An increase in the gas flow rate increases the values of the parameters that quantify the chaotic behavior of the solids motion. This analysis is found to constitute a promising tool to determine flow regime transitions

The spin-spin relaxation time measured from the line width (T 2*) is used to study bonded phase dynamics of two liquid crystal materials in the solid state as a function of temperature. The motion of these two bonded phases is much more restricted than either C-18 or butyl phenyl bonded to the same substrate. Plots ofT 2* vs. 1/T indicate a structural transition of the bonded phase moiety for the two liquid crystal materials but no such change is seen for either C-18 or butyl phenyl over the same temperature range (243–353 K), suggesting a higher degree of association between adjacent bonded moieties for the two liquid crystal materials in comparison to the other two phases. The conclusions from solid-state NMR data coincide with results obtained in earlier chromatographic studies.

Atmospheric pressure plasmas have shown great promise for the treatment of wounds and cancerous tumors. In these applications, the sample is usually covered by a thin layer of a biological liquid. The reactive oxygen and nitrogen species (RONS) generated by the plasma activate and are processed by the liquid before the plasma produced activation reaches the tissue. The synergy between the plasma and the liquid, including evaporation and the solvation of ions and neutrals, is critical to understanding the outcome of plasma treatment. The atmospheric pressure plasma sources used in these procedures are typically repetitively pulsed. The processes activated by the plasma sources have multiple timescales—from a few ns during the discharge pulse to many minutes for reactions in the liquid. In this paper we discuss results from a computational investigation of plasma–liquid interactions and liquid phase chemistry using a global model with the goal of addressing this large dynamic range in timescales. In modeling air plasmas produced by a dielectric barrier discharge over liquid covered tissue, 5000 voltage pulses were simulated, followed by 5 min of afterglow. Due to the accumulation of long-lived species such as ozone and N x O y , the gas phase dynamics of the 5000th discharge pulse are different from those of the first pulse, particularly with regards to the negative ions. The consequences of applied voltage, gas flow, pulse repetition frequency, and the presence of organic molecules in the liquid on the gas and liquid reactive species are discussed.

This report presents the progress made during the fourth (no cost extension) year of this three-year grant aimed at the development of a consistent Lattice Boltzmann formulation for boiling and two-phase flows. During the first year, a consistent LBM formulation for the simulation of a two-phase water-steam system was developed. Results of initial model validation in a range of thermo-dynamic conditions typical for Boiling Water Reactors (BWRs) were shown. Progress was made on several fronts during the second year. Most important of these included the simulation of the coalescence of two bubbles including the surface tension effects. Work during the third year focused on the development of a new lattice Boltzmann model, called the artificial interface lattice Boltzmann model (AILB model) for the 3 simulation of two-phase dynamics. The model is based on the principle of free energy minimization and invokes the Gibbs-Duhem equation in the formulation of non-ideal forcing function. This was reported in detail in the last progress report. Part of the efforts during the last (no-cost extension) year were focused on developing a parallel capability for the 2D as well as for the 3D codes developed in this project. This will be reported in the final report.more » Here we report the work carried out on testing the AILB model for conditions including the thermal effects. A simplified thermal LB model, based on the thermal energy distribution approach, was developed. The simplifications are made after neglecting the viscous heat dissipation and the work done by pressure in the original thermal energy distribution model. Details of the model are presented here, followed by a discussion of the boundary conditions, and then results for some two-phase thermal problems.« less

The dispersion of heavier-than-air aerosol clouds is of great relevance ti the analysis and assessment of hazards in the chemical and petrochemical industries. There are many simple mathematical models for heavy gas dispersion but, in most cases, two-phase dynamics are either ignored or treated in a very simple way, without any convincing scientific justification. In fact almost all of those models which do treat two-phase phenomena rely on the “homogeneous equilibrium” assumption, whether they be for jet dispersion, for gravity dominated dispersion, or for any other aspect of a two-phase release. Here we test the homogeneous equilibrium model against a more sophisticated aerosol approach, in the context of two-phase ammonia clouds released in dry and moist air. It is shown that the simpler model does indeed provide a good description for some envisaged release situations, and guidance is given on where the homogeneous equilibrium model is not likely to be adequate. The homogeneous equilibrium model seems to be adequate for evaluating the dispersion of heavier-than-air clouds containing droplets smaller than 100 μm.

In mathematical models for heavy gas clouds dispersing in the atmosphere, two-phase dynamics is usually modelled using assumptions of homogeneous equilibrium. This implies that the mixture of liquid droplets and gas is homogeneous and in thermodynamic equilibrium at all times. This paper discusses a more rigorous approach for modelling the thermodynamical aspects of heavy gas dispersion. A model is presented for the evaporation and condensational growth of a monodisperse binary droplet population, including also the influence of air entrainment. The model evaluates the thermodynamical evolution of a five-component aerosol mixture, consisting of two-component droplets and a three-component gas. The model has been applied for evaluating two-phase ammonia clouds released in both dry and moist air. The numerical results show the influence on contaminant concentration of the droplet size, the atmospheric moisture and the non-ideality of a liquid solution.

Effects of stereoregularity and crystallization mode on the amorphous phase dynamics are investigated for poly(lactic acid) PLA. An isothermal crystallization from the melt and a cold crystallization are imposed. For each PLA, the cold crystallization leads to the appearance of a less perfect crystalline phase and to an important rigid amorphous fraction RAF content (35%), although only 10% of RAF is generated after crystallization from the melt. Temperature Modulated Differential Scanning Calorimetry is used to determine the Cooperative Rearranging Regions (CRR) size at the glass transition temperature in the mobile amorphous phase MAP. It is shown that the CRR size in the MAP is not modified by the appearance and the spherulite growth. For the intra-spherulite MAP, a confining effect is evidenced, causing an amorphous phase thickness decrease during crystallization, and inducing a drastic CRR size reduction.

The fluid dispensing is one of the key technologies in electronic packing. A novel approach of non-contact fluid dispensing has been proposed based on the principle of gas-liquid two-phase flow. In view of gas-liquid two-phase dynamics, the flow pattern of slug flow can be obtained stably in the microchannel as the flow rate ratio between the gas and liquid is in an appropriate range. The slug flow can generate fluid droplets and gas bubbles and spray them out of the nozzle with uniform interval, accurate volume, good consistency, high controllability and no back haul. This paper carried out the numerical simulation to investigate the gas-liquid two-phase flow in the microchannel for the adhesive dispensing. A 2-D model of microchannel with a diameter for 0.04 mm was established and meshed. The gas-liquid slug flow emerges after iterating over 1 million steps with the gas flow rate for 0.1 m/s, the water flow rate for 0.05 m/s. The wetting property controlled by the contact angle had been discussed to present different liquid materials application. The poor wetting of liquid benefited for conforming droplets shape and avoiding droplets crashing and back haul. While the gas flow rate decreased, the length of liquid droplet and gas bubble increased and decreased, respectively and the total numbers of bubble and droplet decreased in one period. This indicated the fluid parameters have a high relationship with the quantity and volume of droplet.