Showing papers by "University of Electro-Communications published in 1978"
TL;DR: In this article, the spectral properties of in-beam electron impact ionization mass spectra of several amino sugars, which give barely detectable molecular ion peaks by the use of conventional direct inlet probes, are described.
Abstract: Characteristics of in-beam electron impact ionization mass spectra of several amino sugars, which give barely detectable molecular ion peaks by the use of conventional direct inlet probes, are described. The spectra of these compounds almost always exhibited the M + 1 peak and the spectral features were apparently a combination of those of the conventional electron impact spectrum and some major peaks originating from the M + 1 ions. In the case of neamine, effects of the measurement conditions such as the source temperature, ionizing voltage, the position of the sample and time factors on the intensity of the M + 1 peak were examined. When the samples were mixed with ammonium chloride, the M + 1 peaks in the in-beam spectra were completely suppressed, while with aqueous ammonia, the abundance of the M + 1 peaks in creased by several times.
30 citations
TL;DR: A substantial improvement in the fit of analytical to ab initio energies may be obtained by distinguishing between atoms characterized by the same atomic number but having different chemical characteristics, like the oxygen atoms of the phosphate group, on one hand, and the oxygen atom of the sugar rings and the hydroxyl groups, on the other.
Abstract: The sugar–phosphate–sugar complex C10H18O8P, a unit of the polynucleotide chains, was analyzed, making use of 100 conformational energies computed in the Hartree-Fock approximation with a small basis set of Gaussian type orbitals. The geometry of the conformations [which corresponds to the C(2′)-endo deoxy system], the basis set, and the computed total energies are reported in this work. In addition, a number of attempts are presented where we searched for a computationally very simple analytical expression apt to fit, with reasonable accuracy, the computed energies. Lennard-Jones type potential seems to offer an appropriate form capable of reproducing the positions of the maxima and the minima resulting from ab initio computations, but neither the 6-12 nor other similar forms seem to be able to correctly reproduce the intensity of the barriers. Form a details analysis of the barriers to rotation about the bonds O(5′)—C(5′) and C(5′)—C(4′) in terms of nonboned interactions, we found that a substantial improvement in the fit of analytical to ab initio energies may be obtained by distinguishing between atoms characterized by the same atomic number but having different chemical characteristics, like the oxygen atoms of the phosphate group, on one hand, and the oxygen atoms of the sugar rings and the hydroxyl groups, on the other.
29 citations
TL;DR: In this paper, the characteristics of the in-beam electron impact mass spectra of six isomers of undecanol as well as several 1-alkanols have been examined.
Abstract: The characteristics of the in-beam electron impact mass spectra of six isomers of undecanol as well as several 1-alkanols have been examined. In addition to the characteristic ions observed in the conventional electron impact spectra, the [2M+1]+, [2M+1-H2O]+, [2M+1-2H2O]+, [2M-R or R′]+, [2M-H2OR or R′]+, [2M2H2OR or R′]+ and [M+1H2O]+ peaks are common in the in-beam electron impact mass spectra of the undecanol isomers of structure RCH(OH)R′. Deuterium labelling experiments have shown that the extra proton in the protonated dimer ions, [2M+1]+, originates from the hydroxy group. The processes which produce the important peaks in the high m/e regions are discussed.
17 citations
TL;DR: It is shown that the minima of these maps are in excellent agreement with the most stable conformations as obtained from x‐ray crystallographic analysis of nucleic acids and polynucleotides.
Abstract: Conformational energy maps for the four combinations of two consecutive torsional angles of the backbone structure of polydeoxyribonucleotides are presented. Both the C(2′)-endo and the C(3′)-endo conformation of sugar rings were considered. The energies were evaluated with an analytical expression representing the best fit to ab initio energies computed in the Hartree-Fock approximation, and consisting of a contribution from nonbonded interactions of the Lennard-Jones 6-12 type and an intrinsic torsional potential. It is shown that the minima of these maps are in excellent agreement with the most stable conformations as obtained from x-ray crystallographic analysis of nucleic acids and polynucleotides.
14 citations
TL;DR: The results of this study show that the best description of ab initio energies is offered by a potential containing a Lennard‐Jones 6‐12 term and an intrinsic torsional term.
Abstract: In the first paper of this series we showed that the total electronic energy, computed ab initio in the Hartree-Fock approximation for both independent and coupled rotations of the five torsional angles in the sugar–phosphate–sugar complex C10H18O8P, can be reproduced with reasonable accuracy by a Lennard-Jones 6-12 potential, with different attractive and repulsive parameters assigned to the four oxygens of the phosphate group, on one hand, and the four oxygens of the sugar rings and the hydroxyl groups, on the other. The conclusion was reached on the basis of some attempts at the derivation of analytical expressions capable of correctly describing the energies obtained with the quantum mechanical computations. An analysis of the barriers to internal rotation for the angles φ and ψ indicated the possibility of improving the description through addition of further terms, in particular of an intrinsic torsional potential. In order to obtain a fit based on all internal rotations of the sugar–phosphate–sugar molecules, and coupling numerical accuracy with physical significance, we made a study of the possible contributions to the conformational energy: intrinsic torsional energy, electrostatic interactions, London attractions, van der Waals repulsions. The results of this study show that the best description of ab initio energies is offered by a potential containing a Lennard-Jones 6-12 term and an intrinsic torsional term.
14 citations
TL;DR: In this article, cross sections for n-and l-changing collisions of a high-Rydberg atom with a polar molecule are evaluated and found to be of the order of 10/sup -14/--10/sup −11/ cm/sup 2.
Abstract: Cross sections for n- (and l-) changing collisions of a high-Rydberg atom with a polar molecule are evaluated and found to be of the order of 10/sup -14/--10/sup -11/ cm/sup 2/. This is based on the model of the quasifree behavior of an excited Rydberg electron, with its interaction with the polar molecule playing a dominant role, and on the mechanism due to energy transfer from molecular rotation to the excited electron. It is shown that the magnitude of the cross sections drastically increases as the energy defect for the collision process becomes small. The calculated results for a symmetric-top as well as a linear polar molecule are in reasonable agreement with recent experimental findings. The possibility of learning about rotational deexcitation of the polar molecule by an extremely slow electron impact from experimental information on these processes is briefly discussed.
12 citations
TL;DR: The shortest path, shortest spanning tree, complete graph, number of comparisons, expected complexity, and expected complexity are studied.
11 citations
TL;DR: The statistical properties of the level-crossing intervals of Gausslan random process are experimentally studied and the correlation coefficients between successive level- crossing intervals are measured for Gaussian processes having a seventh-order Butterworth power spectral density.
Abstract: The statistical properties of the level-crossing intervals of Gausslan random process are experimentally studied. The probability density functions and variances of the level-crossing intervals and the correlation coefficients between successive level-crossing intervals are measured for Gaussian processes having a seventh-order Butterworth power spectral density.
11 citations
10 citations
TL;DR: The normal modes and frequencies of A 2u species which correspond to the Pseudo-Jahn-Teller active vibration of iron-porphin compound are determined in this article, where the lowest frequency takes almost constant value 227.6 cm -1 on the wide range of the force constant parameter between iron and porphin.
Abstract: The normal modes and frequencies of A 2u species which correspond to the Pseudo-Jahn-Teller active vibration of iron-porphin compound are determined. The lowest frequency takes almost constant value 227.6 cm -1 on the wide range of the force constant parameter between iron and porphin.
7 citations
TL;DR: In this article, the spin Hamiltonian parameters of europium ions in alkali chlorides and bromides were investigated at room and liquid nitrogen temperatures, and the dependence of b 2 0 and b 2 2 on the lattice constant, a, of host crystals was discussed.
TL;DR: In this paper, a system to control a conventional double grating Raman spectrometer (Spex 1400-II) by a small size computer (YHP 21-MX with 16K Memory) is described.
Abstract: A system to control a conventional double grating Raman spectrometer (Spex 1400-II) by a small size computer (YHP 21-MX with 16K Memory) is described. It is designed mainly for an application to a study of phase transitions in crystals. It is shown that some difficulties associated with soft mode spectroscopy using a conventional system can be removed. In particular, fluctuations of the scanning speed are eliminated and sufficient reproducibility is obtained utilizing the Rayleigh scattering profile. The present method improves the signal to noise ratio without requiring a long-term stability of the overall system. Some provisions made for an efficient use of the computer and for a handy analysis of spectra are explained. A few examples are given in the case of a KH2PO4 crystal.
TL;DR: In this article, the authors examined the elastic energy and stability of dispirations for straight lines and circular loops, and showed that the elastic energies of twist, wedge and mixed dispiration lines as well as circular dispiration loops are simply the sum of the self-energies of the dislocation and disclination components.
TL;DR: In this article, the lattice constants of (Pb1-y Ba y )1-x La x Nb2-x/5O6 have been measured by means of x-ray powder analysis over the range of x=0-0.1 and y=0.4.
Abstract: Lattice constants of (Pb1-y Ba y )1-x La x Nb2-x/5O6 have been measured by means of x-ray powder analysis over the range of x=0–0.1 and y=0.4, and the comparison with dielectric measurements for ceramics reveals the existence of the successive transitions between the tetragonal (para), the tetragonal (ferro) and the orthorhombic (ferro) phase. It is also pointed out that the optical anisotropy is likely to depend on the deformations of the octahedra of oxygens.
01 Jan 1978
TL;DR: In this article, a special case of the level-crossing problem is considered, where the successive level crossing points are alternately upcrossing and downcrossing, and the level crossing intervals may mutually be dependent for most cases.
Abstract: The properties of the time interval lengths during which a random process exceeds a certain level are of particular interest for many physical and engineering problems. Some examples of such random processes are the output of a linear or non-linear system to which a white Gaussian noise is applied, semiconductor binary noise, fading of a radio wave, ocean wave and so on. An important quantity of the problem is the distribution density or the variance of the level-crossing interval lengths. Up to now, none of them is known in analytical form but approximations are known applying certain assumptions on the statistical dependences between successive intervals [1,2]. For the zero-crossing problem, which is a special case of the level-crossing problem, MCFADDEN derived two equations regarding the variance and the sums of the correlation coefficients between the lengths of successive but not necessarily adjacent zero-crossing time intervals [3,4]. SATO et al. derived two expressions for the two kinds of variances assuming that the successive level-crossing intervals are mutually independent [5]. However, the successive level-crossing points are alternately upcrossings and downcrossings, and the level-crossing intervals may mutually be dependent for most cases. Therefore we have to take account of those dependences.
23 Aug 1978
01 Jan 1978
TL;DR: In the conventional ICR spectrometer, various RF and DC electric fields are produced by a number of electrodes which compose an ICR cell and the principal functions of these fields are to trap ions inside the cell, to drive ions by cycloidal motion in the direction perpendicular to the static electric and magnetic fields and to make resonant the ions which meet the cyclotron resonance condition as discussed by the authors.
Abstract: Ion cyclotron resonance (ICR) spectrometry has become a useful tool for studying ion chemistry in the gas phase. It utilizes the motion of ions in electric and magnetic fields. In the conventional ICR spectrometer, various RF and DC electric fields are produced by a number of electrodes which compose an ICR cell. The principal functions of these fields are to trap ions inside the cell, to drive ions by cycloidal motion in the direction perpendicular to the static electric and magnetic fields and to make resonant the ions which meet the cyclotron resonance condition. It is desirable that these fields are as uniform as possible in order to obtain quantitative information from the ICR signals. However, in most ICR cells the electric fields are quite inhomogeneous and this frequently makes the interpretation of experimental results difficult.
TL;DR: This method consists of both Discrete Faces Method (DFM) and Interpretive Structural Modeling (ISM), which have been remarked on recently, and takes a particular study that is the classification and evaluation of air pollutional situations in Tokyo's 23 wards.
TL;DR: In this article, an emission current control circuit for ion cyclotron resonance spectrometers has been constructed which maintains a constant beam current in the range 10−11−10−6 A with pulsed grid modulation.
Abstract: An emission current control circuit for ion cyclotron resonance spectrometers has been constructed which maintains a constant beam current in the range 10−11–10−6 A with pulsed grid modulation. It regulates emission currents by automatically adjusting grid bias voltages with reference to a feedback signal. A solid state optical coupler is employed to transmit the feedback signal to a grid biasing circuit having a floating common voltage to accelerate electrons. Control to better than 0.1%/h is possible at any emission current between 10−10 and 10−6 A, and control to 0.3%/h at 10−11 A.