Raman Study of the Effect of NaClO4 and NaI on the Hydrogen-Bonded Structure of Liquid NH3

Abstract

Recent studies^1,2 of the Raman spectra of liquid ammonia have been in disagreement with regard to the assignment of bands in the 3000 cm^?1 region. This region is complicated by Fermi resonance between the ν₁ (A₁) fundamental stretching mode and the 2ν₄ (A₁) overtone of the bending mode. In an effort to help clarify these assignments and to study further the structure of liquid ammonia, it was decided to measure the Raman spectrum of several salt solutions in liquid ammonia.     

Fiber modification by steam-explosion: 13C NMR and dynamic mechanical analysis studies of co-refined wood and polypropylene

Wood-plastic material from a novel reactive processing method (co-refining by steam-explosion) was investigated by ¹³C solid state nuclear magnetic resonance (NMR) and dynamic mechanical analysis (DMA). NMR spectra indicated chemistry of the material changed as a result from co-steam-explosion. It was also observed from NMR analysis that the crystallinity of the cellulose increased in the presence of iPP during steam-explosion co-processing. By using variable contact time cross pulse experiments, the relaxation parameters (T _CH and T _1ρ ) for the constitutive components were evaluated to reveal the level of interactions. T _1ρ values for steam-exploded wood had values similar to those published in literature, which are independent relaxation values for lignin and cellulose. However, for co-steam-exploded wood and iPP, the independent value of lignin relative to the amorphous cellulose was absent. It is proposed that lignin adopts an alternate arrangement during co-steam-explosion processing. This arrangement is transient because the independent relaxation of lignin is recovered after the application of heat during compression molding. DMA demonstrated a mechanical reinforcing effect of the steam-exploded wood without influencing the glass transition of polypropylene for the compression molded co-steam-exploded sample. The paper concludes by describing a hypothetical scheme for a meta-stable interaction of wood bio-polymers and iPP.     

Ultraviolet-Visible Spectroscopic Investigation of Reaction of Rubidium and Tellurium in Liquid Ammonia Solution

The sequential reaction of tellurium with rubidium in liquid ammonia solution has been monitored by ultraviolet-visible spectroscopy. Reaction times for rubidium with tellurium in liquid ammonia were markedly slower than those of sodium and potassium, and the “yellow phase” intermediate was long lived and exhibited a peak at approximately 330 nm with a broad shoulder at about 440 nm. Species formed agree with those previously reported: Rb₂Te, Rb₂Te₂, and Rb₂Te₃. Rb₂Te₂ solution was a violet-blue with absorbance peaks at 285.8, 324.3, 358.0, and 560.0 nm. No evidence of disproportionation reactions for rubidium polytellurides in liquid ammonia was observed.     

Resolution of the O(αs2) shape variable controversy for e+e− annihilation

The differences among recent calculations of the O(α_s²) QCD corrections to shape variable distributions for e⁺e^? annihilation are shown to arise from different underlying definitions of jets and jet observables. In particular, the Caltech (large corrections) and DESY (small corrections) results are not obviously contradictory. We raise questions on the validity of all such calculations for the precise empirical determination of α_s from data for e⁺e^?→ hadrons.     

Transport properties of liquid iron up to 6 Gpa

Abstract

The electronic thermal conductivity λ_e(T, p) is determined by application of the Wiedemann-Frans relation with the Lorens function L(T) as obtained at 1 atmosphere, to electrical conductivity data obtained from two sets of high p, T measurements through the polymorphic phases into the liquid atate of pure Iron. Values of Δλ_e(T, p)/Δp in the liquid state vary between 42. 6 and 52. 4[mW cm^?1 K^?1 GPa^?1].Contributions to variations of the Lorens number L(T, p) are discussed in terms of the density of levels Nd(C) and the changes of the Fermi energy ? with p, T as obtained from data on the thermoelectric power S(T, p) variations combined with the electrical conductivlty u(T, p) variations, both determined from high presaure experimental values for did and liquid iron.     

A monte-carlo/molecular dynamics study of the diffusional recombination kinetics of C(a) + O(a) → CO(g) on Pt(111)

The diffusion constants for C and O adsorbates on Pt(111) surfaces have been calculated with Monte-Carlo/Molecular Dynamics techniques. The diffusion constants are determined to be D_C(T)=(3.4 × 10^?3e^{$\text{?13156}\text{T}$})cm²s^?1 for carbon and D_O(T) = (1.5×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1 for oxygen. Using a recently developed diffusion model for surface recombination kinetics an approximate upper bound to the recombination rate constant of C and O on Pt(111) to produce CO_(g) is found to be (9.4×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1.     

δ2H, δ13C and δ18O from whole wood, α-cellulose and lignin methoxyl groups in Pinus sylvestris: a multi-parameter approach

Novel tree ring parameters – δ¹³C and δ²H from methoxyl groups – have been developed to reconstruct palaeoclimate. Tests with δ¹³C and δ¹⁸O derived from whole wood and cellulose samples, however, indicated differences in the isotopic composition and climate signal, depending on the extracted wood component. We assess this signal dependency by analysing (i) δ¹³C and δ¹⁸O from whole wood and cellulose and (ii) δ¹³C and δ²H from methoxyl groups, using Pinus sylvestris L. growing near Altenkirchen (Germany). Results indicate significant correlations among the time series derived from whole wood, cellulose, and lignin methoxyl groups. Compared with the whole wood samples, δ¹³C from methoxyl groups showed a different and overall lower response to climate parameters. On the other hand, δ²H from methoxyl groups showed high correlations with temperature and was also correlated with ring width, indicating its potential as a temperature proxy. Isotope time series with the highest correlation with climatic parameter were: (i) whole wood and cellulose δ¹³C with growing season precipitation and summer temperature; (ii) methoxyl groups with spring precipitation; (iii) whole wood and cellulose δ¹⁸O correlates with annual evapotranspiration and water balance; and (iv) methoxyl group δ²H with spring temperatures. These findings reveal that multiple climate elements can be reconstructed from different wood components and that whole wood proxies perform comparably to cellulose time series.     

Inclusive Ks0-production in e+e− annihilation at energies of 3.6 to 5.0 GeV

We have measured the production cross section for K_s⁰ in e⁺e^? annihilation from 3.6 to 5.0 GeV center of mass energy. A substantial increase of the K_s⁰ yield is observed around 4 GeV in qualitative agreement with the charm hypothesis.     

Proof of comparable K-pair and π-pair production from time-like photons of 1.5, 1.6, and 1.7 GeV and determination of the K-meson electromagnetic form factor

The observation of 21 K⁺K^? pairs in 38 hadron pair events produced at 1.5, 1.6, and 1.7 GeV total centre-of-mass energies in e⁺e^? annihilations, establishes that time-like photons produce K pairs and π pairs with comparable rates in this energy range. The K-meson electromagnetic form factor at a mean s-value of 2.4 GeV² is measured to be |F_K| = 0.50±0.08. The number of e⁺e^? pairs observed in the same angular and energy range is 5148.     

Observation of associated Kos-electron production in e+e− annihilation

We have observed K^o_s production in e⁺e^? annihilation between 3.6 and 4.4 GeV CMS energy. In the 4.0–4.1 GeV range K^o_s mesons occur correlated with prompt electrons, indicating the formation and weak decay of charmed particle. Within the sensitivity of the experiment, no K^o_s-electron correlation is seen at 3.6 and around 4.4 GeV.     

The energy dependence of σ(e+e− → hadrons) in the total centre-of-mass energy range 1.2 to 3.0 GeV

We have observed 1085 events of the type e⁺e^? → hadrons, in the total centre-of-mass energy range √s = 1.2 to 3.0 GeV. The energy dependence of the total annihilation cross-section, parametrized in the form σ(e⁺e^? → hadrons) = A·sⁿ, is measured to be n = -(1.54_?0.29^+0.17) in the above energy range.     

Effect of high CO2 concentration on char formation through mineral reaction during biomass pyrolysis

O₂/CO₂ combustion has attracted considerable attention as a promising technology for CO₂ capture. Using biomass for fuel is considered carbon neutral, and O₂/CO₂ biomass combustion can mitigate the deleterious environmental effect of greenhouse. In this study, the effect of CO₂, the main component gas in O₂/CO₂ combustion, on the pyrolysis characteristics of biomass is investigated. Cellulose, lignin, and metal-depleted lignin pyrolysis experiments were performed using a thermobalance. Information on the surface chemistry of the chars was obtained by Fourier transform infrared (FTIR) spectroscopy to investigate changes in the surface chemistry during pyrolysis under different surrounding gasses. When the temperature increased to 1073 K at heating rate of 1 K s^?1, the char yield of lignin in the presence of CO₂ increased by about 10% compared with that under Ar. However, for cellulose and metal-depleted lignin, no significant difference appeared between pyrolysis under CO₂ and that under Ar. FT-IR showed that a strong peak corresponding to carbonate ions appeared in the char derived from lignin under CO₂. Therefore, salts such as Na₂CO₃ or K₂CO₃ formed during the lignin pyrolysis under CO₂. At around 1650–1770 cm^?1, a significant difference appeared in the FTIR spectra of chars formed under CO₂ and those formed under Ar. C=O groups not associated with an aromatic ring were found only in chars formed under CO₂. It was suggested that these salts affected the char formation reaction, in that the char formed during lignin pyrolysis under CO₂ had unique chemical bands that did not appear in the lignin-derived char prepared under Ar.     

Vibrational Assignments of Some Monosubstituted Pyridines

Abstract

The infrared spectra of 2-(ortho) and 4-(para) vinyl- and ethyl-pyridines have been analysed in the region 400–4000 cm^?1 in liquid phase. The bands obtained are discussed assuming the molecules under C_s and C_2v point groups. The group sensitive fundamentals are compared with those of similar molecules reported in the literature.     

Perturbative QCD calculation of jet cross sections in e+e− annihilation

We calculate the α_s² to three-jet cross sections in e⁺e^? annihilation in a scheme that uses regulator masses for the infrared and collinear divergences. Using various methods to define the three-jet region, we find that the corrections to the O(α_s) cross sections are large.     

Two-photon exchange in p⊆)p→ℓ+ℓ−X and a comparison with QCD

A thorough study of lepton-pair production from two-photon annihilation in p?)p collisions is presented. The differential cross section is calculated over a large range of energies (27?√s?800 GeV as a function of the dilepton mass M as well as the dilepton transverse momentum Q_T and the Feynman variable x_F. No kinematical approximations (such as the equivalent photon approximation) are made. For Q_T ≈ 0 the two-photon mechanism represents an important fraction of the pp→e⁺e^?X cross section already at ISR energies, whereas at ISABELLE energies it dramatically dominates in the interval 0?Q_T?1 GeV. At ISR energies these conclusions follow from a direct comparison of the two-photon contribution with pp→e⁺e^?X data. For the ISABELLE energy range the expected O(α_s) QCD contribution to pp→?⁺?^?X, corrected for soft gluon radiation to all orders (in leading bilogarithmic approximation), was taken as a reference. At larger Q_T and ISR energies the γγ contribution is negligible, whereas at √s = 800 GeV γγ/QCD? 10–20% almost everywhere. Furthermore, two-photon candidate events from the ISR are shown to be in reasonable agreement with theory. A decomposition of the γγ cross section into contributions from both proton vertices being elastic, inelastic and of mixed configuration is given. The results provide important clues for a future isolation of the two-photon mechanism.     

The order αs2 energy-energy correlation function at small angles

The coefficients that give the small angle (back-to-back) behavior of the energy-energy correlation function in e⁺e^? annihilation are calculated at order α_s² from previous all order, small angle formulas. The purpose is to facilitate comparison with all angle, order α_s² calculations.     

Ultrasound-Assisted Surface-Modification of Wood Particulates for Improved Wood/Plastic Composites

The combined effects of alkali and ultrasound treatment of wood flour on the mechanical properties of polypropylene-based wood/plastic composites (WPCs) were examined. FT-IR measurements confirmed that the alkali treatment removed both hemicellulose and lignin from the wood, and there was an increase in the number of hydroxyl groups on the cellulose surface. This process was promoted by ultrasound treatment. Mechanical testing of injection-molded WPC samples revealed that alkali treatment improved both composite strength and modulus when polypropylene grafted with maleic acid was used as a coupling agent. The strength increase is due to improved adhesion between the fiber and matrix, while improved modulus is due to the removal of lignin and hemicellulose that are not as stiff as cellulose. Polarized optical microscopy showed the presence of well-defined polymer crystals on the surface of the modified wood, and this is also responsible for the improved mechanical properties. It is conclusively demonstrated that the combination of chemical treatment of wood and ultrasound assistance is more effective in improving the mechanical properties of the composites than the use of chemical treatment alone.     

Multiplicity distributions in e+e− annihilations at petra energies

Measurements of the charged multiplicities for hadron production in e⁺e^? annihilation in the center of mass energy range 9–32 GeV have been made. The average charged multiplicity has an energy dependence much stronger than ln s and similar to that reported for pp collisions. Quantitative differences are observed in the magnitude of both the average multiplicity 〈n_ch〉 and the dispersion D_ch for e⁺e^? and pp interactions at the same center of mass energy. 〈n_ch〉 and the ratio 〈n_ch/D_ch in e⁺e^? annihilations are significantly larger than in pp collisions and are found to be in overall agreement with QCD predictions. KNO scaling is seen to be satisfied.     

马尾松木材褐腐降解的红外光谱研究

用傅立叶变换红外光谱(FTIR)研究了马尾松木材被茯苓褐腐菌降解过程中化学成分的变化。测量了木质素和综纤维素的相关红外吸收峰的峰高比值,用湿化学方法测定了未褐腐和不同褐腐时间木材的Klason木质素含量和综纤维素含量,分析了红外吸收峰峰高比值与Klason木质素含量和综纤维素含量的相关性。褐腐15周内,1736和1372cm-1处归属于综纤维素的吸收峰强度逐渐减弱,1510和1225cm-1处归属于木质素的吸收峰强度逐渐增强;但褐腐15周后,1736和1372cm-1处的吸收强度却开始略微增强,1510和1225cm-1处吸收强度略微下降。I1510/I1736,I1510/I1372,I1225/I1736和I1225/I1372与Klason木质素和综纤维素含量之间均存在非常好的线性相关,R2为0.96～0.99。I1736/I1510和I1372/I1510与综纤维素含量之间存在高度线性相关,R2=0.96。结果说明用红外光谱技术可以对木材褐腐过程中的综纤维素含量和Klason木质素含量进行准确分析。