共查询到20条相似文献,搜索用时 10 毫秒
1.
M. B. Krasil’nikov O. S. Vasyutinskii O. Roncero 《Russian Journal of Physical Chemistry B, Focus on Physics》2013,7(2):97-104
A theoretical analysis of the orientation and alignment of the rotational angular momenta of the reactants and products of the Li + HF(v r = 0, j r = 3) → LiF(v, j) + H reaction at a collision energy of E coll = 0.317 eV is performed. The polarization of the angular momentum of the molecules involved in the reaction is based on the technique of spherical tensor operators (state multipoles). Quantum-mechanical calculations of the S-matrix of the reaction are carried out using the wave packet method. In particular, the influence of the orientation of the angular momentum of the HF reactant on the differential cross section is examined. It is shown that the contribution to the differential cross section comes only from be reactants with an angular momentum perpendicular to the reaction plane. In addition, the angular dependence of the orientation and alignment of the angular momenta of the reaction products are examined. It is shown that, for an isotropic distribution of reactant molecules, the orientation of the angular momenta of the products differs from zero only in the direction perpendicular to the reaction plane. Different experimental geometries, based on radiation enhanced multiphoton ionization, are proposed to detect the predicted effects. 相似文献
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Cory O. Rogers Dennis Kaczmarek Tina Kasper Nicole J. Labbe 《Proceedings of the Combustion Institute》2021,38(1):621-629
Understanding the combustion of methyl esters is crucial to elucidate kinetic pathways and predict combustion parameters, soot yields, and fuel performance of biodiesel, however most kinetic studies of methyl esters have focused on smaller, surrogate model esters. Methyl hexanoate is a larger methyl ester approaching the chain length of methyl esters found in biodiesel and has not received as much research attention as other smaller esters. The purpose of this work is to present the first atmospheric pressure combustion data of methyl hexanoate, CH3CH2CH2CH2CH2COOCH3. Mixtures of 2% methyl hexanoate in O2 and N2 are studied using a plug flow reactor at atmospheric pressure, wall temperatures from 573 to 973 K, residence times from roughly 1-2 s., and fuel equivalence ratios of 1, 1.5, and 2. Exhaust gases are analyzed by a gas chromatograph-mass spectrometer system and species mole fractions are presented. The literature model shows satisfactory agreement with the experimental species profiles and improvements for future mechanistic studies are suggested. In particular, this work proposes new unimolecular decomposition pathways of methyl hexanoate to form methanol or methyl acetate. Furthermore, the experiment detected three unsaturated esters that are direct products of the low temperature oxidation chemistry and it provides more insight into branching ratios for the formation of methyl hexanoate radicals and for the decomposition of hydroperoxyalkyl radicals. 相似文献
4.
S. Aeffner T. Reusch B. Weinhausen T. Salditt 《The European physical journal. E, Soft matter》2009,30(2):205-214
We have developed an X-ray scattering setup which allows to study membrane fusion intermediates or other nonlamellar lipid
mesophases by laboratory-scale X-ray sources alone, thus taking advantage of unrestricted beamtime compared to synchrotron
sources. We report results of a study of pure lipid bilayers and phospholipid/cholesterol binary mixtures. Stalks, putative
intermediate structures occurring during the membrane fusion process, can clearly be identified from reconstructed electron
density maps. Phase diagrams of the lyotropic phase behavior of DOPC/cholesterol and DPhPC/cholesterol samples are presented.
If cholesterol is present in moderate concentrations, it can substantially promote the formation of stalks at higher degree
of hydration. In addition, a possibly new phase in DOPC/cholesterol is found at high cholesterol content in the low humidity
range. 相似文献
5.
《Surface science》1995,344(3):L1231-L1238
High resolution electron energy loss spectroscopy (HREELS) has been used to study the adsorption and thermal decomposition of trimethylindium (TMIn) on Ga-terminated GaAs(100) surfaces. HREEL spectra recorded for adsorption at room temperature are dominated by strong CH3 deformation and stretching modes and indicate that the surface species is based on methyl groups. The intensities of these bands decrease with increasing temperature consistent with a primary decomposition route involving the loss of CH3 groups from the surface. A small upward shift in the frequency of the symmetric and asymmetric CH3 deformation modes is also observed with increasing temperature and indicates that decomposition takes place via an exchange reaction in which CH3 groups switch from In to Ga due to the stronger Ga-C bond. At temperatures greater than 350°C, the spectra are dominated by CH2 rocking, deformation and stretching vibrations. The presence of a surface methylene species at elevated temperatures suggests a second, minority decomposition pathway which involves dehydrogenation of surface CH3 groups to CH2. 相似文献
6.
New ionic liquids containing (3-chloro-2-hydroxypropyl)-functionalized pyridinium cations have been synthesized by the ultrasound-assisted, atom-efficient, room temperature reaction of pyridine with acid and 3-chloro-propylene oxide, the acid providing the anionic component of the resultant ionic liquids, and under the ultrasound, a clear yield increase results and a dramatic reduction of the reaction time accompanied by an improved quality of the products occurs. Furthermore, the application of new ionic liquids were tested as solvents in Morita-Baylis-Hillman reaction, in some cases, good results were obtained. 相似文献
7.
L.B. Madsen L.A.A. Nikolopoulos P. Lambropoulos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):67-79
Ab initio time-dependent (TD) calculations of the behavior of positronium (Ps) under strong subpicosecond laser pulses are presented.
The results are compared with results in H through scaling. It is found that a substantial amount of the population can be
found in excited states after the pulse. In the perturbative regime, generalized multiphoton ionization cross-sections are
extracted from the results of the time-dependent calculations. The generalized cross-sections are used to predict the response
of Ps to nanosecond laser pulses at wavelengths of current experimental interest. Beyond the application to Ps, the generality
of the method for extracting generalized cross-sections from TD nonperturbative calculations is discussed.
Received 8 June 1999 相似文献
8.
Optical emission spectroscopy (OES) was used to study the plasma generated by the activation of the gas phase CH4 + H2 both by hot filaments and by a plasma discharge (DC HF CVD) during the nucleation of CVD diamond. The effects of nucleation parameters, such as methane concentration and extraction potential, on the plasma chemistry near the surface were investigated. The density of the diamond nucleation and the quality of the diamond films were studied by scanning electron microscopy (SEM) and Raman scattering, respectively. The OES results showed that the methane concentration influenced strongly the intensity ratio of Hβ-Hα implying an increase of electron mean energy, as well as CH, CH+, C2. A correlation between the relative increase of CH+ and the diamond nucleation density was found, conversely the increase of C2 contributed to the introduction of defects in the diamond nuclei. 相似文献
9.
A. G. Kolesnik S. A. Kolesnik A. A. Kolmakov B. M. Shinkevich 《Russian Physics Journal》2001,44(1):77-81
The results of investigations into the occurrence of extremely low-frequency (ELF) modulation in high-frequency (HF) signals are presented. The seasonal and diurnal behavior of the occurrence of synchronous multichannel (SM) ELF modulation is established. A correlation between the SM ELF modulation occurrence and the presence of sporadic E-layers in the ionosphere is found. 相似文献
10.
针对国家对环境污染及能源有效利用的重视,提出了现有汽车空调存在的问题,通过分析日渐成熟的高效太阳能电池技术、充放电控制技术,特别是具有高光电转化效率材料的不断涌现,以及嵌入式单片机技术的不断创新,为实现汽车空调热电制冷以及太阳能天窗的商业化应用提供了必要的技术支持,从而解决现有的蒸汽压缩制冷所面临的制冷剂替换及耗油问题,实现环境的保护和能源的有效利用。 相似文献
11.
Yu. A. Chernov 《Radiophysics and Quantum Electronics》2002,45(5):358-367
We consider the spatial statistical characteristics of an HF signal and the interdependence of the correlation functions of the field amplitude and phase in the case of oblique reflection from the ionosphere. The amplitude and phase parameters are expressed either in terms of the parameter of ionospheric turbidity, which can be determined most easily, or only in terms of the correlation coefficient of amplitudes at different points. We obtain the expressions for the amplitude and phase correlation functions, which describe well the experimental data. 相似文献
12.
We make a thorough non-covariant analysis of the derivation of the equation of motion for a charged particle, including radiation reaction, by means of a simple model for the charge: a dumbbell. This model and our method to expand retarded quantities, based on complex-variable theory, allow us to avoid some of the usual approximations, so we can show several features of the radiation reaction problem. 相似文献
13.
This paper investigates how well different kinds of fMRI functional connectivity analysis reflect the underlying interregional neural interactions. This is hard to evaluate using real experimental data where such relationships are unknown. Rather, we use a biologically realistic neural model to simulate both neuronal activities and multiregional fMRI data from a blocked design. Because we know how every element in the model is related to every other element, we can compare functional connectivity measurements across different spatial and temporal scales. We focus on (1) psycho-physiological interaction (PPI) analysis, which is a simple brain connectivity method that characterizes the activity in one brain region by the interaction between another region's activity and a psychological factor, and (2) interregional correlation analysis. We investigated the neurobiological underpinnings of PPI using simulated neural activities and fMRI signals generated by a large-scale neural model that performs a visual delayed match-to-sample task. Simulated fMRI data are generated by convolving integrated synaptic activities (ISAs) with a hemodynamic response function. The simulation was done under three task conditions: high-attention, low-attention and a control task ('passive viewing'). We investigated how biological and scanning parameters affect PPI and compared these with functional connectivity measures obtained using correlation analysis. We performed correlational and PPI analyses with three types of time-series data: ISA, fMRI and deconvolved fMRI (which yields estimated neural signals) obtained using a deconvolution algorithm. The simulated ISA can be considered as the 'gold standard' because it represents the underlying neural activity. Our main findings show (1) that evaluating the change in an interregional functional connection using the difference in regression coefficients (as is essentially done in the PPI method) produces results that better reflect the underlying changes in neural interrelationships than does evaluating the functional connectivity difference as a change in correlation coefficient; (2) that using fMRI and deconvolved fMRI data led to similar conclusions in the PPI-based functional connectivity results, and these generally agreed with the nature of the underlying neural interactions; and (3) the functional connectivity correlation measures often led to different conclusions regarding significance for different scanning and hemodynamic parameters, but the significances of the PPI regression parameters were relatively robust. These results highlight the way in which neural modeling can be used to help validate the inferences one can make about functional connectivity based on fMRI data. 相似文献
14.
When a dynamical system is investigated from a time series, one of the most challenging problems is to obtain a model that reproduces the underlying dynamics. Many papers have been devoted to this problem but very few have considered the influence of symmetries in the original system and the choice of the observable. Indeed, it is well known that there are usually some variables that provide a better representation of the underlying dynamics and, consequently, a global model can be obtained with less difficulties starting from such variables. This is connected to the problem of observing the dynamical system from a single time series. The roots of the nonequivalence between the dynamical variables will be investigated in a more systematic way using previously defined observability indices. It turns out that there are two important ingredients which are the complexity of the coupling between the dynamical variables and the symmetry properties of the original system. As will be mentioned, symmetries and the choice of observables also has important consequences in other problems such as synchronization of nonlinear oscillators. (c) 2002 American Institute of Physics. 相似文献
15.
Oprisan SA 《Chaos (Woodbury, N.Y.)》2002,12(1):27-32
We explore the possibility and the limits of extracting the parameters of the model from simulated logistic and Henon time series. For the models considered, the least-squares approach provides accurate values of the recurrence order and polynomial degree along with the model parameters. We found that the number of data points increases the accuracy of the estimation only for noise-free data. With the white noise added to the data, the accuracy could not be improved above a certain threshold that is almost independent of the number of data points. The additive noise flattened the global minimum of the least-squares function such that above a noise threshold it is no longer possible to discern the optimum values of the recurrence order and/or polynomial degree. (c) 2002 American Institute of Physics. 相似文献
16.
In-situ characterisation of the n+-GaAs/HF:Et-OH interface is studied by current-voltage, J(V). The experimental current-potential exhibits the presence of three potential regions, which are attributed to different reaction mechanisms between HF and n+-type GaAs surface. Depending on HF concentration a current peak appears in the J(V) characteristics. Scanning electron microscopy (SEM) images of samples at different point of the J(V) characteristic exhibits different surface morphologies which depend strongly on the electrochemical anodization conditions. 相似文献
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O. M. Artamonov S. N. Samarin A. O. Smirnov 《Journal of Electron Spectroscopy and Related Phenomena》2001,120(1-3):11-26
We suggest applying of the spherical electron mirror in the time-of-flight electron spectrometer with a position sensitive detector in order to increase the effective acceptance solid angle of the spectrometer. The spherical electron mirror is placed near the specimen and it focuses electrons on a position sensitive detector as a converging electron flux. The electron mirror increases the acceptance angle of the spectrometer by a factor of 20. The electron mirror of the spectrometer consists of an inner spherical electrode of the radius R and an outer spherical electrode of the radius 1.1R. The central segment of the inner electrode inside the linear angle of 80° is made of a grid. The detector plate radius is about 0.23R. The acceptance solid angle of the spectrometer with this electron mirror is about 1.1sr, the range of the polar angle of emission is 20°–90° relative to the surface normal, and the range of the azimuth angle of emission at its maximum is ±36° relative to the basic plane of the spectrometer. The design of the spectrometer allows to recover the electron trajectory for each detected electron and to calculate the energy and the emission angle of the electron. The energy resolution of the spectrometer is about 0.2 eV/ns for the electron energy of 10 eV. The energy range is from Emin0.1eUr up to eUr, where Ur is the retarding potential of the electron mirror. The perturbing influence of the grid of the electron mirror limits mainly the angular resolution of the spectrometer and affects relatively slightly the energy resolution. The electron spectrometer with two detectors and two electron mirrors symmetric about the spectrometer axis allows to measure electron pairs in coincidence in a wide range of emission angles and energies with k-resolutions. 相似文献
19.
J. Cejpek 《Czechoslovak Journal of Physics》1966,16(3):186-193
A method is derived for calculating the matrix element of stripping reaction (d,p) in the socalled distorted-wave Born approximation; only Coulomb scattering of incident and outgoing particles is taken into consideration. Coulomb wave functions are expressed by means of integral representation permitting integration over angular variables and, when the radial wave function of the trapped neutron is specially chosen, also calculation of the radial integral for non-zero orbital momentum of the trapped neutron. Relations are given for calculating the differential cross-section of reaction and the polarization of products. The special case, when the orbital momentum of the captured neutron is equal to one or two, is discussed in detail. 相似文献