Insights into the Maillard reaction. The mechanism of Schiff's base formation from the reaction force perspective

Schiff's base formation of the Maillard reaction is described from a theoretical viewpoint. The double proton transfer reaction was investigated within the frame of reaction force analysis in which global and local electronic properties were monitored within reaction regions defined along the reaction coordinate. Calculations based on density functional theory show that Schiff's base formation in the Maillard reaction occurs through an asynchronous double proton transfer, the second proton transfer being the determinant step of the reaction.     

Radiative lifetimes for the A2Σ+ (v′ = 0–7) and D2Σ+ (v′ = 0–5) Rydberg states of NO

Intensities for the γ(A²Σ⁺?→?X²Π), ε(D²Σ⁺?→?X²Π) and (D²Σ⁺?→?A²Σ⁺) bands for NO have been calculated using the Molecular Quantum Defect Orbital (MQDO) methodology. Radiative lifetimes for the A²Σ⁺ and D²Σ⁺ vibrational Rydberg states have also been determined. The present results are in excellent accord with measurements available in the literature. Additionally, predictions for a number of unknown intensities and radiative lifetimes are made, given their potential usefulness.     

CO2 production in the bromate‐1,4‐cyclohexanedione oscillatory reaction

NMR and GC/MS spectroscopy of the organic extracts of the oscillatory bromate‐1,4‐cyclohexanedione reaction illustrate the presence of ring‐opening products 5‐(dibromomethylene)‐2(5H)‐furanone, (E)‐5,5,5‐tribromo‐4‐oxo‐2‐pentenoic acid, and dibromoacetic acid, particularly at elevated temperatures. The loss of a carbon atom from the six‐membered ring after ring opening led to gas formation and such a process became more vigorous at >60 °C, with the direct observation of bubbles in a stirred batch reactor. Gravimetric experiments confirm that the amount of carbon dioxide gas produced increases rapidly with reaction temperature. Parallel experiments suggest that the ring‐opening process involves the oxidation of brominated benzoquinones by bromate. Copyright © 2010 John Wiley & Sons, Ltd.     

A statistical model for predicting thermal chemical reaction rate

A simple model based on the statistics of individual atoms [Europhys. Lett. 94 40002 （2011）] or molecules [Chin. Phys. Lett. 29 080504 （2012）] was used to predict chemical reaction rates without empirical parameters, and its physical basis was further investigated both theoretically and via MD simulations. The model was successfully applied to some reactions of extensive experimental data, showing that the model is significantly better than the conventional transition state theory. It is worth noting that the prediction of the model on ab initio level is much easier than the transition state theory or unimolecular RRKM theory.     

Study of the structure of unstable nuclei through the reaction experiments

Along with the development of the radioactive nuclear beam facility, the study of the structure of unstable nuclei has progressed rapidly over the last few decades. Due to the weakly binding property, the structure information of the unstable nuclei comes primarily from the scattering or reaction experiments. Therefore it would be very important to understand clearly the reaction mechanism involved in the experiment. We outlined here the major reaction mechanisms which are adequate to the study of unstable ...     

碳化硅合成反应动力学研究

基于经典轨迹法研究了碳化硅合成反应C(3Pg) SiO(X1∑ ,V=0,1;J=0)→SiC(X1∑ ) O(3Pg)的动力学.该反应存在阈能,反应截面均存在一个极大值和最佳反应能量.当SiO(X1∑ )分别处于V=0、J=0和V=1、J=0状态时,反应阈能分别约为1.2552×103kJ.mol-1和1.1297×103kJ.mol-1,反应截面极大值分别为5.3742×10-3nm2和5.1824×10-3nm2,而最佳初始碰撞能Et(the Optimal InitialCollision Translation Energy)分别为3.3472×103kJ.mol-1和3.7656×103kJ.mol-1.在SiC的最佳产率区(即最佳反应能区),通过反应物的振动激发并不能使SiC产率明显提高,因此基态下SiC合成反应的最佳能区即为该反应的最佳产率区.     

2H-氮杂卓衍生物迁移反应的光谱学特征

氮杂卓化合物存在1H-,2H-,3H-和4H-共4个互变异构体,其中,2H-,3H-系统是最重要的。2H-氮杂卓母体化合物很不稳定,4位存在叔-丁基,并且环上含有丙硫基(PrS-)取代基的2H-氮杂卓,不仅发生H迁移,也能发生PrS-迁移,向较稳定的3H-氮杂卓异构化。以2,7-二甲氧基-4-甲基-2H-氮杂卓为原料,通过与Pr-SH的取代反应,合成7-甲氧基-4-甲基-2-PrS-2H-氮杂卓,并讨论分析产物的 迁移反应。通过IR、¹H NMR、¹³C NMR、MS检测表明,在室温条件下,4位存在甲基的2H-氮杂卓衍生物,选择性地发生 PrS-迁移,生成3H-氮杂卓,而且此异构化反应速度比叔-丁基存在时的情况更快。     

The width of the 5.11 MeV state in 10B and isovector parity mixing

We review estimates for effects of parity mixing on the α-capture of vector polarized ⁶Li to the 5.16 MeV, 2⁺, T = 1 state in ¹⁰B. The cross section depends on the ⁶Li polarization direction because of isovector parity mixing with the 5.11 MeV, 2^?, T = 0 state. The effect is enhanced due to isospin conservation. The α-width of the 5.11 MeV state, an important parameter for calculating the enhancement, has been measured to be 0.98 ± 0.07 keV. The consequences of parity mixing are reevaluated using best available values for the relevant parameters.     

Evaporation residue excitation functions from fusion of 63Cu with 65Cu

Mass distributions of evaporation residues from the fusion of ⁶³Cu + ⁶⁵Cu have been measured at seven excitation energies from 55 to 105 MeV in a single irradiation experiment. They are interpreted as a mixture of residues produced by single nucleon evaporation cascades and cascades including α-particle evaporation. Compound nuclei with an average excitation energy of 55 MeV ($\text{51.5 ≦ E}{}^1\text{≦ 59}\text{MeV}$) are still found to have a probability as high as 0.3 % for decaying by emission of a single nucleon. The low-energy behaviour of the excitation function can be interpreted as a fusion barrier effect. The parameters of this barrier are determined. The evaporation residue cross section at higher energies is shown to be limited by the fission of the compound nucleus.     

Elastic pion-deuteron scattering near the 3-3 resonance

The elastic scattering of positive pions by deuterium has been studied at seven energies between 82 MeV and 292 MeV laboratory kinetic energy in the angular range between 30° and 130° (lab). The results are compared to recent relativistic three-body calculations.     

Proton yields from quasielastic pion scattering on 27Al and 208Pb

A singles measurement of the quasielastic scattering of 255 MeV pions by ²⁷Al and ²⁰⁸Pb has been made. The measured values for the ratio R of π⁺ and π^? induced cross section, averaged over all measured angles of 2.2 ± 0.2 and 1.5 ± 0.1 for ²⁷Al and ²⁰⁸Pb respectively are substantially below the classical impulse approximation value of 11. A semiclassical nucleon charge exchange model is described for singles and coincidence measurements and is compared with the measured proton spectra. The comparison indicates that the singles proton spectra are dominated by events other than the quasielastic process whereas the coincidence data reported earlier and compared with the present calculations support the quasielastic interpretation. A strongly decreasing dependence of R on A for coincidence measurements may be interpreted as supporting the view that recoil nucleon charge exchange plays an important role in the quasielastic knockout process.     

Light particle emission and projectile fragmentation in 14N + 12C

Quasi-complete in-plane correlations are measured between two heavy fragments (¹²C, ¹²C; ¹²C, ¹³C) which leave a missing mass such as n, p, d or p + n in ¹⁴N + ¹²C at 48 MeV. The use of two position-sensitive telescopes in coincidence allows an observation of data over 675 combinations of angles. The strongest coincidence yield concerns the ¹²C + ¹³C + p exit channel in which the target (¹²C) is left either in its ground state or in its first excited state ($\text{σ ? 40}\text{and}\text{15}\text{mb}$ respectively). No significant yield is found for the dissociations ¹²C + ¹²C + d, ¹²C + ¹³N + n or ¹²C + ¹⁰B + α at this energy.Using the reconstructed proton velocities, we obtain a source pattern in the rapidity plot which is roughly centered in the so-called mid-rapidity region. On the other hand, the Dalitz plot exhibits an enhancement of events which could be due to a projectile fragmentation $\text{(}{}^{14}\text{N}\text{→}{}^{13}\text{C}\text{+}\text{p}\text{)}$ via a real or virtual excitation energy of 8.7 MeV.     

High-resolution investigation of the 112Sn(p,d)111Sn reaction

The ¹¹²Sn(p, d)¹¹¹Sn reaction was studied at a proton energy of 27.45 MeV. The outgoing deuterons were momentum analyzed with an Enge split-pole spectrograph and recorded with position-sensitive solid-state detectors with a total resolution between 12 and 16 keV. Angular distributions were compared with DWBA calculations in order to extract l-values, spectroscopic factors, single-quasiparticle energies and occupation probabilities. In the gross structure between 3 and 6 MeV, which was interpreted as being due to the pickup of deeply bound neutrons, several discrete peaks were also found with an angular distribution characteristic for l = 1 or 4 transfer. The excitation of core-coupled states was investigated by performing two-step DWBA calculations. The results of the present experiment are compared with previous experimental results and with number-projected BCS calculations.     

High-spin states and yrast isomerism in 153Er

Energy levels in ¹⁵³Er have been populated in the reaction ¹⁴⁴Sm(¹²C. 3n)¹⁵³Er. Isotopically enriched targets were bombarded with 53–65 MeV ¹²C ions and the emitted γ-ray and conversion electron spectra were investigated. From studies of excitation functions. γ- coincidences, γ-ray multiplicities, delayed γ-radiation and angular distributions, the level scheme of ¹⁵³Er has been constructed. The properties of the energy levels are discussed and compared with the results of calculations with a deformed shell model. The remarkable similarities and some important discrepancies of the level structure, when compared with adjacent, N = 85 nuclides, are emphasized.     

The (n, α) reaction on 11B induced by 14.4 MeV neutrons

The ¹¹B(n, α)⁸Li reaction has been studied at 14.4 MeV in a geometry that allows simultaneous detection of the emitted and recoil particles. The angular distributions have been measured for the transitions to the ground and first excited states of the ⁸i nucleus and compared with PWBA for knock-on and heavy-particle pick-up processes. The total cross sections for the respective transitions have been deduced.     

Search for the parity-forbidden heavy-particle width Γ′dα of the Ex = 3.562 MeV state in 6Li

Alpha-particle capture by deuterium has been investigated at excitation energies in ⁶Li close to the J^π = 0⁺, T = 1, E_x, = 3.562 MeV state. A search for resonance γ-rays from this state has yielded a negative result and an upper limit for the heavy-particle width Γ′_dα ≦ 0.017 eV.     

Polarization in n-d scattering at 14.2 MeV

The angular distribution of the analyzing power in ${}^2\text{H(}\text{n}\text{,}\text{n}{}^2\text{H}$ elastic scattering has been measured at a neutron energy of 14.2 MeV in the angular range 50° to 152° c.m. Neutrons with a polarization of approximately 0.5 were obtained from the ${}^3\text{H(}\text{d}\text{n}\text{)}{}^4\text{He}$ reaction at a deuteron energy of 140 keV and lab emission angle of 82°. The ${}^3\text{H(}\text{d}\text{n}\text{)}{}^4\text{He}$ reaction was induced by vector polarized douterons obtained from a source of polarized ions. The latter was of a conventional “atomic beam” type. The results show good agreement with the data on the charge symmetric $\text{p}\text{+}\text{d}$ process at a proton energy of 14.5 MeV. Comparison is also made with the theoretical calculations of Doleschall and of Pieper and a good agreement is found.