Absolute Reaction Rate Research Articles

Hydrogen diffusion and hydrogen embrittlement in iron (steel)

This article examines the diffusion of hydrogen (H-diffusion) and the temperature dependences of the diffusion coefficient of hydrogen (DH) in the metal (M)-hydrogen system. The metal used was iron and low-alloy steel. Taking into account experimental data on hydrogen diffusion in the Fe-H and steel-H systems, the main diffusion parameters were calculated and compared. It is shown that the temperature dependences of the hydrogen diffusion coefficient in metal samples in a one-stage reaction under isothermal conditions are described by the Arrhenius equation. For some M-H systems, experimental data show a deviation of the diffusion coefficient from the ideal one calculated using the Arrhenius equation. This discrepancy can be eliminated using the statistical theory of absolute reaction rates. For the temperature range 25–1250 oС, the pre-exponential coefficient and activation energy of hydrogen diffusion in a body-centered cubic (bcc) lattice of iron (α–Fe) were calculated using the Arrhenius equation. These parameters make it possible to describe the dependence of the rate of hydrogen diffusion in a metal on temperature and to predict the behavior of hydrogen diffusion when changing the conditions of the kinetic process (concentration of substances, pressure, structure, composition, etc.). Tabular values of the calculated pre-exponential factor and activation energy of hydrogen diffusion in previously studied iron-based samples are presented. The temperature dependences of the hydrogen diffusion coefficient in a lattice of iron α–Fe can be divided into low-temperature and high-temperature regions. The calculated diffusion parameters of hydrogen in the metal lattice for the low-temperature 25– 800 oC and high-temperature 800–1250 oC regions differ markedly from each other. In addition, these calculated values are significantly influenced by the structure and composition of the metal. We also studied the diffusion of hydrogen in α-iron using ab initio density functional calculations. Molecular dynamics calculations using transition state theory were used. The calculated diffusion coefficient of hydrogen in α-Fe is consistent with previously obtained experimental data. Hydrogen embrittlement (HE) is considered using internal pressure, hydrogen enhanced localized plasticity (HELP) and hydrogen enhanced decohesion embrittlement (HEDE) theories.

Scavenging of Superoxide Radical Anion by Fluorinated Organosilicon Additives

We have explored a set of structurally related fluorinated and non-fluorinated organosilicon additives and quantified their rates of reaction with the superoxide radical anion O2 •−. using rapid-scan cyclic voltammetry. Absolute reaction rate measurements in acetonitrile solvent show that O2 •− reacts with the fluorinated OS compounds with bimolecular rate constants k BM more than 1000x larger than k BM for the reaction between O2 •− and ethylene carbonate. We further identified the products of reaction of a model OS compound using multiple nuclear magnetic resonance (NMR) methods and with gas chromatography/mass spectroscopy. Chemical analysis measurements show that addition of potassium superoxide KO2 to a model fluorinated OS compound produces only one product. Our results indicate that that OS compounds improve battery performance by rapidly scavenging O2 •− in a way that produces a stable product and reduces or eliminates the competing chemical pathways associated with carbonate breakdown. These results provide new insights into how chemical structure impacts critical chemical reactions and may guide the design of new additives that further improve battery safety and stability.

Viscosities of iodobenzene + n-alkane mixtures at (288.15–308.15) K. Measurements and results from models

Kinematic viscosities were measured for iodobenzene + n-alkane mixtures at (288.15–308.15) K and atmospheric pressure. The corresponding dynamic viscosities (η) were also determined using density data previously obtained in our laboratory. This set of data was employed to calculate Δη (deviations in absolute viscosity) and quantities of viscous flow. In addition, the correlation equations: McAllister, Grunberg-Nissan, Fang-He, and the Bloomfield-Dewan's model were applied to the systems: iodobenzene, or 1-chloronaphthalene, or 1,2,4-trichlorobenzene, or methyl benzoate or benzene or cyclohexane + n-alkane. It is remarkable that, within the Bloomfield-Dewan's model, residual Gibbs energies were calculated using DISQUAC with interaction parameters available in the literature. From the dependence of UVmE (isochoric molar excess internal energy) and Δη with n (the number of C atoms of the n-alkane), it is shown that the loss of fluidization of mixtures containing iodobenzene, 1,2,4-trichlorobenzene, or 1-chloronaphthalene when n increases can be ascribed to a decrease, upon mixing, of the number of broken interactions between like molecules. The breaking of correlations of molecular orientations characteristic of longer n-alkanes may explain the decreased negative Δη values of benzene mixtures with n = 14,16. The replacement, in this type of systems, of benzene by cyclohexane, leads to increased positive Δη values, probably due to the different shape of cyclohexane. On the other hand, binary mixtures formed by an aromatic polar compound mentioned above and a short n-alkane show large structural effects and large negative Δη values.From the application of the models, it seems that dispersive interactions are dominant and that size effects are not relevant on η values. The free volume model provides good results for most of the systems considered, since deviations are less than 6% for 20 mixtures from the 29 solutions under study, and only 4 systems show deviations higher than 10%, with a maximum deviation of 15%. Results improve when, within the Bloomfield-Dewan’s theory, the contribution to η of the absolute reaction rate model is also considered.

Molecular Modeling of Supercritical Processes and the Lattice—Gas Model

The existing possibilities for modeling the kinetics of supercritical processes at the molecular level are considered from the point of view that the Second Law of thermodynamics must be fulfilled. The only approach that ensures the fulfillment of the Second Law of thermodynamics is the molecular theory based on the discrete–continuous lattice gas model. Expressions for the rates of the elementary stage on its basis give a self-consistent description of the equilibrium states of the mixtures under consideration. The common usage today of ideal kinetic models in SC processes in modeling industrial chemistry contradicts the non-ideal equation of states. The used molecular theory is the theory of absolute reaction rates for non-ideal reaction systems, which takes into account intermolecular interactions that change the effective activation energies of elementary stages. This allows the theory to describe the rates of elementary stages of chemical transformations and molecular transport at arbitrary temperatures and reagent densities in different phases. The application of this theory in a wide range of state parameters (pressure and temperature) is considered when calculating the rates of elementary bimolecular reactions and dissipative coefficients under supercritical conditions. Generalized dependencies are calculated within the framework of the law of the corresponding states for the coefficients of compressibility, shear viscosity, and thermal conductivity of pure substances, and for the coefficients of compressibility, self- and mutual diffusion, and shear viscosity of binary mixtures. The effect of density and temperature on the rates of elementary stages under supercritical conditions has been demonstrated for a reaction’s effective energies of activation, diffusion and share viscosity coefficients, and equilibrium constants of adsorption. Differences between models with effective parameters and the prospects for developing them by allowing for differences in size and contributions from the vibrational motions of components are described.

Room temperature rate coefficients for the reaction of chlorine atoms with a series of volatile methylsiloxanes (L2‐L5, D3‐D6)

AbstractThe kinetics of chlorine (Cl) atom reactions with a series of volatile methylsiloxanes (VMS) including hexamethyldisiloxane (L2), octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were investigated in relative rate experiments at room temperature and atmospheric pressure. The experiments were carried out in a 0.2 m3 PFA Teflon chamber, employing proton‐transfer‐reaction time‐of‐flight mass spectrometry (PTR‐ToF‐MS) as the chemical‐analytical tool. The following relative and absolute reaction rate coefficients were obtained using isoprene as reference compound (kVMS/kisoprene; kVMS × 1010 cm3 molec−1 s −1): L2 (0.32 ± 0.02; 1.31 ± 0.21), L3 (0.38 ± 0.00; 1.56 ± 0.23), L4 (0.48 ± 0.01; 1.98 ± 0.29), L5 (0.54 ± 0.03; 2.22 ± 0.34), D3 (0.14 ± 0.02; 0.56 ± 0.13), D4 (0.26 ± 0.01; 1.05 ± 0.16), D5 (0.36 ± 0.02; 1.46 ± 0.22), D6 (0.39 ± 0.02; 1.61 ± 0.25). The following relative and absolute reaction rate coefficients were obtained using toluene as reference compound (kVMS/ktoluene; kVMS × 1010 cm3 molec−1 s −1): L2 (1.59 ± 0.18; 0.95 ± 0.14), L3 (2.25 ± 0.14; 1.35 ± 0.16), L4 (2.38 ± 0.01; 1.43 ± 0.14), L5 (3.57 ± 0.11; 2.14 ± 0.22), D3 (0.87 ± 0.01; 0.52 ± 0.05), D4 (1.48 ± 0.12; 0.89 ± 0.11), D5 (2.02 ± 0.15; 1.21 ± 0.15), D6 (2.54 ± 0.11; 1.52 ± 0.17). Our data confirm that reactions with Cl atoms need to be taken into account when assessing the decomposition of VMS in Cl‐rich tropospheric environments.

Extent of Inhibition of Malonic Acid on the Fermentation of Soursop Juice: A Thermodynamic Evaluation

The fermentation of soursop juice as substrate by Saccharomyces cerevisiae (yeast) was investigated to obtain certain useful thermodynamic parameters. This was achieved by the determination of the effects of temperature, substrate and inhibitor on the rate of carbon (IV) oxide (CO2) production. The extent of inhibition was examined by the addition of malonic acid inhibitor. The results indicate that the rate of fermentation of soursop juice increased in proportion with temperature (optimum 36oC), substrate (optimum 50%v/v) and malonic acid (optimum 30%v/v) up to a limit and decreased. This suggests that the reaction takes place in two steps (equilibrium and decomposition steps). The thermodynamic parameters determined are: enthalpy, ∆H* 151.14 kJmol-1; entropy of activation, ∆S* 275.359 Jmol-1k-1; Gibb’s free energy of activation, ∆G* -752.21 kJmol-1 and Equilibrium constant Keq, 1.33 respectively. The results show that the enthalpy value is positive indicating that the fermentation process is endothermic while the activation energy is same as the enthalpy. The entropy value is positive corroborating the positive enthalpy value. The fermentation process is spontaneous as shown by the negative change in free energy. These values were subsequently used to obtain by calculation Arrhenius constant A, 1.51x1023; orientation factor P, 1.41x10-34 and the collision frequency, Z, 1.07x1011 respectively. The calculated A and the P values obtained on the basis of collision theory and absolute reaction rate theory (or transition state theory), respectively show that the collision factor is of the order of 1011 min-1, about half that of gaseous molecules that can only be attained by an induced reduction in activation energy by a catalyst. The equilibrium constant value K suggests that the intermediate complex is rather interacting more with the substrate and also showing that only a limited amount of the substrate is converted to product. The equilibrium constant K is observed to be 1.33dm3mol-1 and not significantly far from unity implying that G* can be conveniently equated with the change in free energy at standard conditions. Finally, the type of inhibition was found to be uncompetitive from the extrapolated Lineweaver-Burk plots and did not bring about marked decrease in the rate of fermentation as expected.

Resolving the Mechanistic Complexity in Triarylborane-Induced Conjugate Additions

Previous studies have shown that the catalytically active species in the Lewis acid-catalyzed addition reactions of allyl silanes or silyl enol ethers to carbonyl compounds or Michael acceptors are often silylium-carbonyl adducts rather than the adducts of the carbonyl group with the Lewis acid used for the induction of the reaction. Indirect evidence for such catalyst variations has so far been derived from double-label crossover experiments and comparisons of absolute reaction rates. We have now performed a detailed investigation on the kinetics and mechanism of the triarylborane-initiated conjugate addition reactions of allylsilanes and silyl enol ethers to α,β-unsaturated carbonyl compounds. NMR spectroscopic monitoring of such reactions gave rise to sigmoidal kinetic profiles, allowing us to directly follow the change of the catalytically active Lewis acid from triarylboranes in the induction period to silylium ions during the main part of the reaction. Crossover experiments and the isolation of four- and five-membered cyclic intramolecular trapping products provided further insight into the mechanism. DFT calculations of various mechanistic variants and kinetic modeling elucidated the operation of a complex reaction network, which rationalizes the experimental observations.

Theoretical Study on the Kinetics of the Rubisco Carboxylase Reaction by a Model Based on Quantum Chemistry and Absolute Reaction Rate Theory.

The rate of the Rubisco carboxylase reaction is evaluated by statistical mechanics and hybrid density functional theory (DFT). The Rubisco molecular model given by Kannappan et al. was modified and used in the present calculation. The activation energies of CO2 addition reaction, H2O addition reaction, C2–C3 bond scission, and C2 protonation are estimated. We calculated the turnover number (TON) for each of the four reaction steps based on a revised absolute reaction rate theory, which became applicable to soft matter reactions. The molecular parameters used in TON calculations were obtained by DFT calculations. The TON of the total Rubisco reaction was finally evaluated using rate equations. The calculation in a vacuum gave the total TON to be around 5 × 10–5, which was much lower than the experimental value. The DFT calculation in water solvent gave the total TON to be around 0.1, which agreed reasonably well with experimentally reported values (∼2.71). The rate-limiting process was the scission reaction. The present calculation showed that both the phosphate groups in the substrate accelerate each reaction step. The present calculation showed that a more comprehensive molecular model including enolization and quantum chemical methods is necessary to make a more precise reaction model including the irreversibility of some reactions.

Characterization of Neutron Reaction Rates in Different Irradiation Channels of the CNESTEN’s TRIGA Mark II Research Reactor

The National Center for Energy, Sciences and Nuclear Techniques (CNESTEN)’s Training Research and Isotope Production General Atomics (TRIGA) Mark II is a pool-type light water moderated and cooled research reactor operating at a maximum steady state thermal power of 2 MW. The reactor was designed to be used as a training facility for reactor operators, neutron activation analysis, isotopes production, and for implementing different reactor physics experiments. This article deals with the numerical and experimental characterization of reaction rates (RRs) in different irradiation channels inside the CNESTEN’s TRIGA Mark II research reactor, located in Rabat/Morocco. The main objective of this study is to validate the calculated neutron RRs against the measured ones and to prove that the new TRIPOLI-4 model of the reactor is capable to reproduce the measured quantities. Therefore, the measurements were carried out using the neutron activation technique and gamma spectrometry measurements. Preliminary simulations were performed with TRIPOLI-4 transport Monte Carlo code to establish the experimental design and set up for activation foils experiments. The selected set of foils with known characteristics were irradiated, at different power levels, inside the irradiation facilities of the TRIGA reactor. The resulting activities were evaluated via <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> spectrometry measurements. Normalized calculated and measured RRs were compared, and a good agreement was shown for most nuclides, which indicates that the new detailed TRIPOLI-4 model of the TRIGA reactor can accurately predict the relative experimental RRs values. Further work is ongoing to analyze absolute RR values, as well as to carry measurements in other irradiation channels.

Oxidative Damage of Aliphatic Amino Acid Residues by the Environmental Pollutant NO3·: Impact of Water on the Reactivity.

The rate of oxidative damage of aliphatic amino acids and dipeptides by the environmental pollutant nitrate radical (NO3·) in an aqueous acidic environment was studied by laser flash photolysis. The reactivity dropped by a factor of about four for amino acid residues with secondary amide bonds and by a factor of up to nearly 20 for amino acid residues with tertiary amide bonds, compared with that in acetonitrile. According to density functional theory studies, the lower reactivity is due to protonation of the amide moiety, whereas in neutral water, hydrogen bonding with the amide should have little impact on the absolute reaction rate compared with that in acetonitrile. This finding can be rationalized by the high reactivity and broad reaction pattern of NO3·. Although hydrogen bonding involving the amide group raises the energies associated with some electron transfer processes, alternative low-energy pathways remain available so that the overall reaction rate is barely affected. The undiminished high reactivity of NO3· toward aliphatic amino acid residues in a neutral aqueous environment highlights the health-damaging potential of exposure to the combined air pollutants nitrogen dioxide (NO2·) and ozone (O3).

Thermodynamic stability of microheterogenic states in Fe – Mn – C melts

Possibility of existence of microheterogeneous states in Fe – Mn – C melts was analyzed carried out according to the concepts of chemical thermodynamics. Microheterogeneous state of a chemically inhomogeneous Fe – Mn – C melt was understood as presence of dispersed Fe – C particles in it, which are suspended in Mn – C environment and separated from it by interface. Hypothesis of microheterogeneous state of Fe – Mn – C melts is supported by numerous experimental data on their thermodynamic and physical properties. Identification of anomalies in temperature dependences of physical properties of Fe – Mn – C melts made it possible to determine temperature values above which the melt superheating treatment (MST) leads to destruction of microheterogeneity, i.e., the liquid – liquid structure transition (LLT) in the melt. LLT is understood by authors as a structural transition “microheterogeneous melt – homogeneous solution” and this is expressed in destruction of microheterogeneous state when the melt is heated to a temperature determined for each composition (MST). This paper describes a method for theoretical determination of temperature range where microheterogeneous state of the Fe – Mn – C melt is thermodynamically stable. Thermodynamic stability of dispersed Fe – C particles in the Mn – C medium was estimated according to the equations proposed by Kaptay for a regular solution. It was assumed that interface between the melt of dispersed Fe – C particles with sizes from 2 to 34 nm, distributed in the Mn – C dispersion medium and separated from it by an interface with increased carbon content. This result of the assessment is consistent with the data on size of the structural units of a viscous flow obtained earlier within framework of the theory of absolute reaction rates.

Small activation entropy bestows high-stability of nanoconfined D-mannitol* *Project supported by the National Natural Science Foundation of China (Grant Nos. 52001319, 52071327, 51922102, 51771216, and 51701230), the Natural Science Foundation of Zhejiang Province, China (Grant Nos. LR18E010002), the Ningbo 2025 Science and Technology Innovation Project (Grant No. 2019B10051), and the Natural Science Foundation of Ningbo City (Grant No. 202003N4354).

It has been a long-standing puzzling problem that some glasses exhibit higher glass transition temperatures (denoting high stability) but lower activation energy for relaxations (denoting low stability). In this paper, the relaxation kinetics of the nanoconfined D-mannitol (DM) glass was studied systematically using a high-precision and high-rate nanocalorimeter. The nanoconfined DM exhibits enhanced thermal stability compared to the free DM. For example, the critical cooling rate for glass formation decreases from 200 K/s to below 1 K/s; the T g increases by about 20 K–50 K. The relaxation kinetics is analyzed based on the absolute reaction rate theory. It is found that, even though the activation energy E* decreases, the activation entropy S* decreases much more for the nanoconfined glass that yields a large activation free energy G* and higher thermal stability. These results suggest that the activation entropy may provide new insights in understanding the abnormal kinetics of nanoconfined glassy systems.

Frontier Orbitals, Combustion and Redox Transfer from a Fermionic-Bosonic Orbital Perspective

Oxygenations are highly exergonic, yet combustion of organic matter is not spontaneous in an atmosphere that is 21% O2. Electrons are fermions with a quantum spin number s of 1/2ħ. An orbital containing a single electron with s = 1/2 is fermionic. Orbitals can contain a maximum of two electrons with antiparallel spins, i.e., spin magnetic quantum numbers ms of 1/2 and -1/2. An orbital filled by an electron couple has s = 0 and bosonic character. The multiplicity of a reactant is defined as |2(S)| + 1 where S is the total spin quantum number. The Wigner spin conservation rules state that multiplicity is conserved. The transmission coefficient κ of absolute reaction rate theory also indicates the necessity for spin conservation. Burning is fermionic combustion that occurs when sufficient energy is applied to a bosonic molecule to cause homolytic bond cleavage yielding fermionic products capable of reaction with the bifermionic frontier orbitals of triplet multiplicity O2. Neutrophil leucocytes kill microorganisms by bosonic combustion and employ two mechanisms for changing the multiplicity of O2 from triplet to singlet. Microorganisms, composed of bosonic singlet multiplicity molecules, do not directly react with bifermionic O2, but are highly susceptible to electrophilic attack by bosonic electronically excited singlet molecular oxygen (1O2*). Hydride ion (H-) transfer is the common mode of cytoplasmic redox metabolism. Bosonic transfer of an orbital electron couple protects from damage by obviating fermionic reaction with bifermionic O2. Bosonic coupled electron transfer raises the consideration that quantum tunneling might be involved in facilitating such redox transfer.

Multipole-moment effects in ion-molecule reactions at low temperatures: part I - ion-dipole enhancement of the rate coefficients of the He+ + NH3 and He+ + ND3 reactions at collisional energies Ecoll/kB near 0 K.

The energy dependence of the rates of the reactions between He+ and ammonia (NY3, Y = {H,D}), forming NY2+, Y and He as well as NY+, Y2 and He, and the corresponding product branching ratios have been measured at low collision energies Ecoll between 0 and kB·40 K using a recently developed merged-beam technique [Allmendinger et al., ChemPhysChem, 2016, 17, 3596]. To avoid heating of the ions by stray electric fields, the reactions are observed within the large orbit of a highly excited Rydberg electron. A beam of He Rydberg atoms was merged with a supersonic beam of ammonia using a curved surface-electrode Rydberg–Stark deflector, which is also used for adjusting the final velocity of the He Rydberg atoms, and thus the collision energy. A collision-energy resolution of about 200 mK was reached at the lowest Ecoll values. The reaction rate coefficients exhibit a sharp increase at collision energies below ∼kB·5 K and pronounced deviations from Langevin-capture behaviour. The experimental results are interpreted in terms of an adiabatic capture model describing the rotational-state-dependent orientation of the ammonia molecules by the electric field of the He+ atom. The model faithfully describes the experimental observations and enables the identification of three classes of |JKMp〉 rotational states of the ammonia molecules showing different low-energy capture behaviour: (A) high-field-seeking states with |KM| ≥ 1 correlating to the lower component of the umbrella-motion tunnelling doublet at low fields. These states undergo a negative linear Stark shift, which leads to strongly enhanced rate coefficients; (B) high-field-seeking states subject to a quadratic Stark shift at low fields and which exhibit only weak rate enhancements; and (C) low-field-seeking states with |KM| ≥ 1. These states exhibit a positive Stark shift at low fields, which completely suppresses the reactions at low collision energies. Marked differences in the low-energy reactivity of NH3 and ND3—the rate enhancements in ND3 are more pronounced than in NH3—are quantitatively explained by the model. They result from the reduced magnitudes of the tunnelling splitting and rotational intervals in ND3 and the different occupations of the rotational levels in the supersonic beam caused by the different nuclear-spin statistical weights. Thermal capture rate constants are derived from the model for the temperature range between 0 and 10 K relevant for astrochemistry. Comparison of the calculated thermal capture rate coefficients with the absolute reaction rates measured above 27 K by Marquette et al. (Chem. Phys. Lett., 1985, 122, 431) suggests that only 40% of the close collisions are reactive.

Activation Entropy as a Key Factor Controlling the Memory Effect in Glasses.

As opposed to the common monotonic relaxation process of glasses, the Kovacs memory effect describes an isothermal annealing experiment, in which the enthalpy and volume of a preannealed glass first increases before finally decreasing toward equilibrium. This interesting behavior has been observed for many materials and is generally explained in terms of heterogeneous dynamics. In this Letter, the memory effect in a model Au-based metallic glass is studied using a high-precision high-rate calorimeter. The activation entropy (S^{*}) during isothermal annealing is determined according to the absolute reaction rate theory. We observe that the memory effect appears only when the second-annealing process has a large S^{*}. These results indicate that a large value of S^{*} is a key requirement for observation of the memory effect and this may provide a useful perspective for understanding the memory effect in both thermal and athermal systems.

Nanoparticles Size in Fe&lt;sub&gt;73.5&lt;/sub&gt;Cu&lt;sub&gt;1&lt;/sub&gt;Mo&lt;sub&gt;3&lt;/sub&gt;Si&lt;sub&gt;13.5&lt;/sub&gt;B&lt;sub&gt;9&lt;/sub&gt; Melt

The size of the nanoparticles participating in the viscous flow and the diffusion coefficient were calculated using statistical mechanical theory of absolute reaction rates and the Arrhenius equation. As experimental data, temperature dependence of the kinematic viscosity and density of Fe73.5Cu1Mo3Si13.5B9 melt was used. At a temperature of 1600 K, after the melt is overheated above the critical temperature Tk = 1770 K, the nanoparticles size decreases from 0.92 to 0.47 nm, and the diffusion coefficient increases from 2.4·10-10 to 4.5·10-10 m2·s-1.

Characterization of the neutron spectra in three irradiation channels of the JSI TRIGA reactor using the GRUPINT spectrum adjustment code

Reference neutron fields in irradiation facilities are crucial for experimental research work in nuclear science and technology in general, and at the fundamental level for the measurement of neutron cross sections and validation of evaluated cross-section data. Monte Carlo particle transport techniques in conjunction with state-of-the-art nuclear data libraries are becoming the reference in the broad context of nuclear reactor analysis, and are extensively used for detailed computational characterization of irradiation facilities, including the calculation of neutron spectra. However, adjustment of the neutron spectra based on experimental data is still required.In this work we present the characterization of the neutron spectra in the three most important irradiation channels of the JSI TRIGA reactor with different spectral characteristics, as an important step in developing the experimental capabilities of the reactor for the purpose of nuclear data validation through activation dosimetry measurements. In the first part of this work we performed detailed Monte Carlo calculations of the neutron spectra, comparing the results obtained using different nuclear data libraries. In the main part of this work we employed the JSI developed GRUPINT spectrum adjustment code for the characterization of the neutron spectra, on the basis of the calculated neutron spectra and measured reaction rate ratios. A comprehensive overview of the methodology employed in the code and its abilities is given.We observe that a positive compensation of up to 10 % in the thermal part of the spectrum is needed, while no compensation is needed in the epithermal and fast parts. Absolute neutron flux levels were computed from the adjusted neutron spectra and absolute reaction rate measurements, and compared to the results of a previous analysis using only the Monte Carlo calculations. The work presented in this paper represents the basis for future experimental and analytical work, in particular extending the scope of the measured capture and threshold dosimetry nuclear reactions, to support a thorough characterization of the neutron spectra in the irradiation channels of the reactor. This effort will enable the JSI TRIGA reactor to support a broad scope of experiments for fundamental research as well as development or testing activities at the highest level.

Temperature-Resolved Proton Transfer Reactions of Biomolecular Ions.

Temperature-resolved proton transfer reactions of multiply-protonated angiotensin I, disulfide-intact and -reduced lysozyme, and ubiquitin ions to primary, secondary and aromatic amines were examined in the gas phase. Absolute reaction rate constants for the proton transfer were determined from the intensities of the parent and product ions in mass spectra. Dramatic changes were observed in the distribution of product ions and the reaction rate constants. In particular, the rate constants for disulfide-intact lysozyme ions changed more drastically with the change in charge state and temperature compared to the corresponding values for disulfide-reduced ions. Proton transfer reactions were enhanced or suppressed as the result of the formation of complexes between the ions with gaseous molecules, which is related to changes in their conformation with changing.

Immunologic Effects of Sirolimus in Patients With Vascular Anomalies.

Emerging data have suggested that sirolimus may be a treatment option for complicated vascular anomalies (VAs). The present study aimed to investigate the immunologic effects of sirolimus treatment for 6 months in patients with VAs. Blood samples obtained from the patients enrolled in 2 multicenter studies to investigate the efficacy of sirolimus for VAs before and after sirolimus treatment for 6 months were used. Data for total white blood cell count, absolute lymphocyte count, serum immunoglobulins (Igs) levels (IgG, IgA, IgM), lymphocyte proliferation assays with mitogens including phytohemagglutinin and concanavalin A, and flow cytometric analysis of lymphocyte subsets were evaluated. A total of 18 patients with VAs receiving sirolimus treatment were included in the study. Comparisons of white blood cell, absolute lymphocyte count, IgG, IgA, IgM, and reaction rates of phytohemagglutinin and concanavalin A revealed no significant differences before and after treatment. No significant differences were observed in the absolute counts of lymphocyte subtypes before and after treatment, except for regulatory T-cell counts, which were significantly decreased after treatment. Severe infections were not observed during sirolimus treatment. The immunologic parameters assessed in the present study were hardly affected by sirolimus treatment for 6 months in patients with VAs.

Measurement and correlation of density and viscosity of binary mixtures of fatty acid (methyl esters + methylcyclohexane)

The thermodynamics properties of the mixtures of biodiesel and petroleum-based fuel are useful for the research of blending fuels. Biodiesel is mainly consisting of fatty acid alkyl esters. Densities and viscosity for the binary mixtures of three fatty acid methyl esters (methyl decanoate, methyl dodecanoate and methyl tetradecanoate) with methylcyclohexane (MCH) were measured at 7 temperatures from 293.15 to 323.15 K and at atmospheric pressure. Excess molar volumes and viscosity deviations of the three binary systems have been correlated and fitted to Redlich-Kister equation. The change of enthalpy, entropy and Gibbs energy of activation for the flow process for the binary mixtures were calculated on the basis of Eyring’s absolute reaction rate theory. The experimental data and correlated results could provide important information for the research of the blends of biodiesel and diesel oil.