Heat release rate as represented by [OH] × [CH2O] and its role in autoignition

Data from a recent instantaneous, simultaneous, high-resolution imaging experiment of Rayleigh temperature and laser induced fluorescence (LIF) of OH and CH₂O at the base of a turbulent lifted methane flame issuing into a hot vitiated coflow are analysed and contrasted to reference flames to further investigate the stabilization mechanisms involved. The use of the product of the quantified OH and semi-quantified CH₂O images as a marker for heat release rate is validated for transient autoigniting laminar flames. This is combined with temperature gradient information to investigate the flame structure. Super-equilibrium OH, the nature of the profiles of heat release rate with respect to OH mole fraction, and comparatively high peak heat release rates at low temperature gradients is found in the kernel structures at the flame base, and found to be indicative of autoignition stabilization.     

Comparison of the calculated electronic structures of [111] and [001] GaAs/AℓxGa1-xAs semiconductor superlattices

A theoretical comparison of the electronic structures of long-period (about 300 Å) N_GaAs×N_AℓGaAs GaAs/Aℓ_0.3Ga_0.7As superlattices grown along the [111] direction and superlattices grown along the [001] direction is presented. Almost all qualitative features of the theoretical results are in good agreement with experiments by Hayakawa et al. The observed optical transition enhancement in the [111]-oriented quantum-well structures is caused by the topological difference in the superlattices, and is only partly due to the fact that the heavy holes in the [111] superlattices have larger transverse effective masses, and therefore have larger two-dimensional valence band densities of states.     

Spin-wave resonance in [Co x Ni1 − x ]N and [Co x P1 − x ]N gradient films

Gradient films of ferromagnetic 3d metals with prescribed magnetic potential profile along the film thickness are obtained. It is found that the spin-wave resonance spectrum in these films is characterized by anomalous dependences of resonance fields of spin-wave modes H _r on the mode number: H _r(n) ～ n, H _r(n) ～ n ^2/3.     

[15N]Methacetin-und [15N]Ammoniumtest zur Leberfunktionsprüfung im Kindesalter

The stable isotope content of samples of precipitation and of the river water throughout the Piracicaba basin in Brazil was measured over a two-year period. The isotope values of precipitation follow a consistent pattern of relatively depleted values of both deuterium and oxygen 18 during the rainy summers and enriched ones during the dry winters, with all values aligned slightly above the Global Meteoric Water Line. The isotopic composition of the river water throughout the basin shows a remarkable spatial coherence and much smaller scatter of data than those of the precipitation. The isotope composition of river water is close to that of the precipitation in the rainy season, however, with a consistent lower d-excess value by 1‰–2‰. This is attributed to evaporative water loss in the basin, in part an expression of the recycling of water due to the anthropogenic activity in the region. The more divergent values are recorded during high-water stages in the rivers. In many cases, the floods during the beginning of the rainy season are characterized by an enrichment of the heavy isotopes and lower d-excess values when compared to the precipitation, with the opposite situation later in the rainy season. This is interpreted as resulting from the watershed/riverflow interaction pattern, and it thus suggests that the isotope composition can monitor the hydrologic situation in the basin and its changes.     

π-SCF and INDO calculations and the absorption,polarized excitation and circular dichroism spectra of [4]-helicenes

The absorption and circular dichroism spectra of (-)d-1,12-dimethyl-benzo[c]phenanthrene-5-acetic acid are reported, together with the polarized excitation and fluorescence spectra of the parent hydrocarbon, [4]-helicene. The transition energies of 1,12-dimethyl-[4]-helicene calculated in the π-SCF approximation, and the corresponding dipole and rotational strengths obtained by the dipole-velocity method, show that the optical isomer studied has the M-configuration with the stereochemical form of a segment of a left-handed helix. Analogous calculations in the INDO approximation using both the dipole-velocity and the dipole-length procedure with separate consideration of the one-centre and the two-centre transition moment integrals, indicate that the more satisfactory dipole and rotational strengths are obtained in the two-centre dipole-velocity formulation. The appearance of σ → π* transitions at higher energies limits the application of the π-SCF procedure, but the INDO method is found to place these transitions at too low an energy.     

15N-Markierung von Plasmaaminosäuren nach oraler Applikation von [15N]Glycin, [15N]Leucin und [15N]Hefeprotein-Thermitase-Hydrolysat

For the biosynthetic preparation of ¹⁴C-erucic acid (C₂₁H₄₁COOH) by means of rape plants cv. sollux the plants were supplied with ¹⁴CO₂ and additionally fed with ¹⁴C-Sodium acetate after anthesis. After saponification of the extracted lipids the erucic acid was isolated and purified. The substance was identified by gas chromatography. The incorporation of the applied radioactivity (34 MBq ¹⁴CO₂; 37 MBq¹⁴C-natrium acetate) into the fatty acids amounted to 1,2 per cent. The eruric acid could be isolated from the fatty acids mixture with a specific radioactivity of 1,001 MBq/mmol and a purity of 97,2 per cent.     

UV–Vis and NMR spectroscopic investigations on effective and selective non-covalent interactions between fullerenes and calix[6]arene

Ground state non-covalent interactions between a macro cyclic calixarene receptor, namely, 4-tert-butylcalix[6]arene (1), and fullerenes (C₆₀ and C₇₀) were studied in toluene medium by absorption spectrophotometric method. Absorption band due to the charge transfer (CT) transition have been observed in the visible region between fullerenes and 1. Utilizing the CT absorption bands, various important physicochemical parameters like oscillator strength, resonance energy, transition dipole strength of the fullerene-1 complexes and ionization potential of 1 is determined in present investigations. From Jobs method of continuous variation, it is observed that both C₆₀ and C₇₀ form stable 1:1 complexes with 1. The most fascinating feature of the present study is that 1 binds selectively C₇₀ compared to C₆₀ as obtained from binding constant (K) data of C₆₀–1 (K_C60–1) and C₇₀–1 (K_C70–1) complexes, i.e., K_C60–1 = 32,400 dm³·mol^? 1 and K_C70–1 = 110,000 dm³.mol^? 1 and selectivity (K_C70–1/K_C60–1) = 3.4. ¹H NMR analysis provides very good support in favor of strong binding between C₇₀ and 1.     

Langmuir–Blodgett films and optical second-harmonic generation of a crowned [60]fulleropyrrolidine

The Langmuir and Langmuir–Blodgett (LB) films of a novel crowned [60]fullero-pyrrolidine (CFP) were produced in different conditions. Macroscopic second-harmonic generation of the LB film was investigated by means of AM1 Hamiltonian as well as experiments. The monolayer LB film displayed a periodic fringe pattern. A linear dependence of second-harmonic intensity on the number of layers was observed. The second-order molecular susceptibility χ⁽²⁾ and hyperpolarizability β were evaluated to be 3.2×10⁻⁸ and 8.3×10⁻²⁹ esu. Received: 21 October 1999 / Revised version: 30 March 2000 / Published online: 2 August 2000     

6H-SiC（0001）-6[KF（]3[KF）]×6[KF（]3[KF）]R30°重构表面的同步辐射角分辨光电子能谱研究

利用同步辐射角分辨光电子能谱（SRARPES）对6H-SiC（0001）-6[KF（]3[KF）]×6[KF（]3[KF）] R30°重构表面的电子结构和表面态进行了研究.通过鉴别价带谱中来自于体态的信息,可以推断出重构表面的费米能级位于体态价带顶之上（2.1±0.1）eV处.实验测出的体能带结构与理论计算的结果较为符合.在重构表面上发现三个表面态,分别位于结合能-0.48 eV（S₀）,-1.62 eV（S₁）和-4. 关键词： 角分辨光电子能谱 碳化硅（SiC） 电子结构 表面态     

Characteristic effects of substituent and external pressure on group-inclusion complexation with p-sulfonatocalix[8]arene and γ-cyclodextrin

By synthesizing unique nitroxide probes (α-substituted phenyl-2,4,6-trimethoxybenzyl(t-butyl)nitroxide), we have shown that p-sulfonatocalix[8 Sueishi Y, Negi M, Kotake Y. Influence of temperature, pressure, and pH on the group-inclusion equilibrium in water soluble calixarenes. Bull Chem Soc Jpn. 2007;80:1932–1938. doi: 10.1246/bcsj.80.1932[Crossref], [Web of Science ®] , [Google Scholar]]arene (Calix-S8) and γ-cyclodextin (γ-CD) form electron spin resonance spectroscopically separable group-inclusion complexes (α-substituted phenyl-in (R-in) and t-butyl-in complexes) and determined the group-inclusion constants of Calix-S8 and γ-CD. Using nitroxide probes, we have examined the effects of substituent and external pressure on group-inclusion complexation with Calix-S8 and γ-CD. Experiments on pressure dependence enabled us to calculate the reaction volume (Δ V) for R-in and t-butyl-in complex formations. Δ V for group-in complexation with Calix-S8 had negative values. In contrast, Δ V values for γ-CD showed positive values, which is responsible for the repelled water molecules in the CD cavity. The characteristic pressure effects on group-in complexation suggest that group recognition by γ-CD is sensitive when compared with that by Calix-S8.     

2-[2-[4-[2-[2-[1,3-Dihydro-1,1-bis(4-hydroxyphenyl)-3-oxo-5-isobenzofuranthioureidyl]ethylaminocarbonyl]ethyl]phenyl] ethylamino]-5′-N-ethylcarboxamidoadenosine (FITC-APEC): A fluorescent ligand for A2a-adenosine receptors

The fluorescein conjugate, FITC-APEC (2-[2-[4-[2-[2-[1,3-dihydro-1,1-bis(4-hydroxyphenyl)-3-oxo-5-isobenzofuranthioureidyl]ethylaminocarbonyl]ethyl] phenyl]ethylamino]-5-N-ethylcarboxamidoadenosine), is a novel ligand derived from a series of functionalized congeners that act as selective A_2a-adenosine receptor agonists. The binding of FITC-APEC to bovine striatal A_2a-adenosine receptors measured by fluorescence techniques was saturable and of a high affinity, with aB _max of 2.3±0.3 pmol/mg protein andK _D of 57±2 nM. TheK _D value estimated by fluorescence was consistent with theK _i (11±0.3 nM) obtained by competition studies with [³H]CGS 21680. Additionally, theB _max value found by FITC-APEC measurement was in agreement withB _max values obtained using radioligand binding. FITC-APEC exhibited rapid and reversible binding to bovine striatum. The potencies of chemically diverse A_2a-adenosine receptor ligands estimated by inhibition of FITC-APEC binding were in good agreement with their potencies determined using radioligand binding techniques (r=0.97,P=0.0003). FITC-APEC binding was not altered by purine derivatives that do not recognize A_2a-adenosine receptors. These findings demonstrate that the novel fluorescent ligand FITC-APEC can be used in the quantitative characterization of ligand binding to A_2a-adenosine receptors.     

单轴[110]应力硅电子迁移率

基于k·p微扰法研究单轴[110]应力作用下硅的导带结构,获得单轴[110]应力硅的导带底能量及电子有效质量.在此基础上,考虑电子谷间、谷内及电离杂质散射,采用弛豫时间近似计算单轴[110]应力硅沿不同晶向的电子迁移率.结果表明：单轴[110]应力作用下硅的电子迁移率具有明显的各向异性.在[001]、[110]及[110]输运晶向中,张应力作用下电子沿[110]晶向输运时迁移率有较大的增强,由未受应力时的1 450 cm²·Vs^-1提高到2 GPa应力作用下的2 500 cm²·Vs^-1.迁移率增强的主要原因是电子有效质量的减小,而应力作用下硅导带能谷分裂导致的谷间散射几率的减小对电子迁移率的影响并不显著.     

Periodic trends governing the interactions between impurity atoms [H–Ar] and α-U

The binding energies, geometries, charges and electronic structures of a series of impurity atoms [H–Ar] interacting with the α-U lattice in various configurations were assessed by means of density functional theory calculations. Periodic trends governing the binding energy were highlighted and related to the electronic properties of the impurity atoms, with some consideration given to the band-structure of α-U. The strongest bound impurity atoms include [C, N, O] and [Si, P, S]. The general trends in the binding energy can be reproduced by a simple parameterisation in terms of the electronegativity (charge-transfer) and covalent radius (elasticity theory) of the impurity atom. The strongest bound atoms deviate from this model, due to their ability to bind with an optimum mixture of covalency and ionicity. This last point is evidenced by the partial overlap of the impurity atom p-band with the hybrid d–/f-band of α-U. It is expected that the trends and general behaviour reported in this work can be extended to the interactions of impurity atoms with other metallic systems.     

Classification of interference-fading tolerant Φ-OTDR signal using optimal peak-seeking and machine learning [Invited]

A simple and effective interference-fading tolerant method for phase-sensitive optical time-domain reflectometry(Φ-OTDR) using optimal peak-seeking is proposed. This method can reconstruct the vibration signal with high fidelity under the premise of using only an ordinary single-mode sensing fiber without changing the structure of the traditional Φ-OTDR system. Based on the data after interference suppression, we applied different machine learning models to recognize the invasive events category. The promising results show potential applications of Φ-OTDR equipment and future implementation with machine learning algorithms.     

UV光谱研究[Cp-Fe-Cp]BF4和[Cp-Fe-Naph]BF4的光解动力学及机理

本文测定了两种新型阳离子光聚合引发剂二茂铁四氟硼酸盐（[Cp-Fe-Cp]BF4)和环戊二烯基－铁－萘四氟硼酸盐（[Cp-Fe-Naph]BF4)在二氯甲烷和环氧氯丙烷中的紫外－可见吸收光谱，研究了紫外光照射对吸收光谱的影响，通过实时紫外－可见吸收光谱分析，研究了两种光引发剂在环氧氯丙烷中的光解动力学。发现二者的吸收光谱随光照时间的变化规律一致，而且光解反应均为一级反应，速率常数分别为0.72和0.65min^-1，从而提出了二茂铁四氟硼酸盐的光引发机理。     

Electron phonon interactions and superconductivity in α ′ -TTF[Pd(dmit)2]2

A simple model is developed to understand superconductivity in α ^′ -TTF[Pd(dmit)₂]₂. We include electron-intra molecular and intermolecular phonon interactions as the mechanism of superconductivity. Intramolecular vibrations included are the eight symmetric A_g modes of the Pd(dmit)₂ molecule. Intermolecular vibrations included are the longitudinal acoustic and transverse acoustic (LA and TA) modes of the Pd(dmit)₂ column. All the electron-phonon coupling constants are calculated from first principles. We find that largest el-intramolecular vibration coupling is to the A_g mode with the highest frequency (1449 cm^-1). The el-intermolecular coupling to the LA mode is found to be larger than the total el-intramolecular couplings. We also find el-(TA)phonon coupling to be at least an order of magnitude smaller than el-(LA)phonon coupling. Estimate of superconducting transition temperature is comparable to experimental result. We also provide a detailed discussion, employing the results of recent numerical calculations on two-chain Hubbard model and the specific material parameters, on the relative importance of el-ph and Coulomb-origin mechanisms of superconductivity in α ^′ -TTF[Pd(dmit)₂]₂ and TTF[Ni(dmit) ₂ ] ₂ . Received 29 March 2001 and Received in final form 7 August 2001     

1H, 13C and 15N NMR Studies of Protonation in Imidazo[1,2-α]Pyrimidine and Derivatives

We have studied1 the protonation behaviour of several cardiotonic polyazaheterocycles and recently shown that the 2-arylimidazo[l,2-a]pyrimidine (3a) undergoes protonation at the imidazo nitrogen (Nl). These investigations have utilised the shielding of acarbon nuclei and increases in ¹³C-¹H or ¹H-¹H couplings that occur on protonation of a heterocyclic nitrogen. We now report unequivocal protonation studies of the parent heterocycle, imidazo[1,2-a]pyrimidine (l), and its 2-aryl derivative (3b) which have allowed the effect of 2-aryl substitution on protonation to be determined. ¹⁵N NMR spectroscopy was employed to determine the protonation site of (1) in a titration study with H2SO4. In addition the N-methyl quaternary salts (21, (4) and (5) were prepared and ¹⁵N, ¹³C and ¹H chemical shifts measured so as to provide unambiguous substituent effects uncomplicated by possible proton transfers.