Comparative Studies of Phase-Cycling Schemes for Multiple π-Pulse Sequences

Recently, a new phase cycling scheme was introduced by this laboratory for use in biological solid-state NMR experiments involving multiple π-pulses with characteristics that suggested it may enhance the sensitivity of these kind of experiments (Y. Li and J. N. S. Evans, 1995,Chem. Phys. Lett.241,79 and Erratum, 1995,ibid.246,527; Y. Li and J. N. S. Evans, 1996,J. Magn. Reson. B111,296). The new sequence followed the supercycled concept proposed a decade ago for heteronuclear decoupling experiments. In this paper, more detailed experiments demonstrate that the claim of enhanced sensitivity was unfounded, and in fact the supercycle proposed differs little from the established XY-8 and XY-16 based supercycles.     

Cryptanalysis of a chaos-based cryptosystem with an embedded adaptive arithmetic coder

In this paper,we analyse a new chaos-based cryptosystem with an embedded adaptive arithmetic coder,which was proposed by Li Heng-Jian and Zhang J S (Li H J and Zhang J S 2010 Chin.Phys.B 19 050508).Although this new method has a better compression performance than its original version,it is found that there are some problems with its security and decryption processes.In this paper,it is shown how to obtain a great deal of plain text from the cipher text without prior knowledge of the secret key.After discussing the security and decryption problems of the Li Heng-Jian et al.algorithm,we propose an improved chaos-based cryptosystem with an embedded adaptive arithmetic coder that is more secure.     

Excitation of plasma waves by an externally applied electromagnetic wave to a nonuniform classical plasma

Radiation-driven plasma wave equations (RWE's) are derived from the basic dynamical plasma equations through restaining the external radiation source terms and significant nonlinear terms under the simplified assumptions used by Zakharov [1]. Excitation processes of the transverse plasma waves, Langmuir waves by an externally applied electromagnetic wave to a nonuniform unmagnetized plasma are investigated by means of rough numerical simulations based on RWE's. The results show that the amplitude of the transverse plasma waves is sensitive to their effective damping rate and that the radiation-induced density profile modification looks like a step, which are in qualitative agreement with analytical results.Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 8, pp. 959–987, August, 1996.One of the authors (Li) wishes to thank V.L. Ginzburg, E. Mjølhus, B. Thidé, N.S. Erokhin, J.Y. Liu, J.W. Lee, T.D. Carozzi, and J. Bergman for helpful oral discussions on this topic. Li also wants to thank M. Matsuoka for the kind hospitality during his year-long stay at RIKEN, where this work was completed.     

Scattering of Stark-decelerated OH radicals with rare-gas atoms

We present a combined experimental and theoretical study on the rotationally inelastic scattering of OH (X²Π_3/2, J = 3/2, f) radicals with the collision partners He, Ne, Ar, Kr, Xe, and D₂ as a function of the collision energy between ～70 cm^?1 and 400 cm^?1. The OH radicals are state selected and velocity tuned prior to the collision using a Stark decelerator, and field-free parity-resolved state-to-state inelastic relative scattering cross sections are measured in a crossed molecular beam configuration. For all OH-rare gas atom systems excellent agreement is obtained with the cross sections predicted by coupled channel scattering calculations based on accurate ab initio potential energy surfaces. This series of experiments complements recent studies on the scattering of OH radicals with Xe [J.J. Gilijamse, S. Hoekstra, S.Y.T. van de Meerakker, G.C. Groenenboom, G. Meijer, Science 313, 1617 (2006)], Ar [L. Scharfenberg, J. K?os, P.J. Dagdigian, M.H. Alexander, G. Meijer, S.Y.T. van de Meerakker, Phys. Chem. Chem. Phys. 12, 10660 (2010)], He, and D₂ [M. Kirste, L. Scharfenberg, J. K?os, F. Lique, M.H. Alexander, G. Meijer, S.Y.T. van de Meerakker, Phys. Rev. A 82, 042717 (2010)]. A comparison of the relative scattering cross sections for this set of collision partners reveals interesting trends in the scattering behavior.     

Single-oscillator model and determination of optical constants of spray pyrolyzed amorphous SnO<Subscript>2</Subscript> thin films

It has recently been shown that growth of a multilayer structure with one or more delta-layers at high temperature leads to spreading and asymmetrization of the dopant distribution [see, for example, E.F.J. Schubert, Vac. Sci. Technol. A. 8, 2980 (1990), A.M. Nazmul, S. Sugahara, M. Tanaka, J. Crystal Growth 251, 303 (2003); R.C. Newman, M.J. Ashwin, M.R. Fahy, L. Hart, S.N. Holmes, C. Roberts, X. Zhang, Phys. Rev. B 54, 8769 (1996); E.F. Schubert, J.M. Kuo, R.F. Kopf, H.S. Luftman, L.C. Hopkins, N.J. Sauer, J. Appl. Phys. 67, 1969 (1990); P.M. Zagwijn, J.F. van der Veen, E. Vlieg, A.H. Reader, D.J. Gravesteijn, J. Appl. Phys. 78, 4933 (1995); W.S. Hobson, S.J. Pearton, E.F. Schubert, G. Cabaniss, Appl. Phys. Lett. 55, 1546 (1989); Delta Doping of Semiconductors, edited by E.F. Schubert (Cambridge University Press, Cambridge, 1996); Yu.N. Drozdov, N.B. Baidus', B.N. Zvonkov, M.N. Drozdov, O.I. Khrykin, V.I. Shashkin, Semiconductors 37, 194 (2003); E. Skuras, A.R. Long, B. Vogele, M.C. Holland, C.R. Stanley, E.A. Johnson, M. van der Burgt, H. Yaguchi, J. Singleton, Phys. Rev. B 59, 10712 (1999); G. Li, C. Jagadish, Solid-State Electronics 41, 1207 (1997)]. In this work analytical and numerical analysis of dopant dynamics in a delta-doped area of a multilayer structure has been accomplished using Fick's second law. Some reasons for asymmetrization of a delta-dopant distribution are illustrated. The spreading of a delta-layer has been estimated using example materials of a multilayer structure, a delta-layer and an overlayer.     

The Three Dimensional Non-conforming Finite Element Solution of the Chapman–Ferraro Problem

We demonstrate the feasibility of using a non-conforming, piecewise harmonic finite element method on an unstructured grid in solving a magnetospheric physics problem. We use this approach to construct a global discrete model of the magnetic field of the magnetosphere that includes the effects of shielding currents at the outer boundary (the magnetopause). As in the approach of F. R. Toffolettoet al.(1994,Geophys. Res. Lett.21, 7) the internal magnetospheric field model is that of R. V. Hilmer and G.-H. Voigt (1995,J. Geophys. Res.) while the magnetopause shape is based on an empirically determined approximation (1997, J. Shueet al.,J. Geophys. Res.102, 9497). The results is a magnetic field model whose field lines are completely confined within the magnetosphere. The presented numerical results indicate that the discrete non-conforming finite element model is well-suited for magnetospheric field modeling.     

Elucidation of the structure of a highly efficient blue emitting lithium boron 2-(2-hydroxyphenyl) benzoxazole

We have studied the new blue electroluminescent material (compound 1) synthesized from the reaction of 2-(2-hydroxyphenyl)benzoxazole with LiBH₄ according to Tao's procedure [J. Am. Chem. Soc. 121 (1999) 9447; Appl. Phys. Lett. 75 (1999) 1665] Compound 1 showed the UV and the PL peak at 366 and 432 nm, respectively. The manufactured device (ITO/compound 1(600 Å)/Al) showed the EL peak at 412 nm. However, the structure of compound 1 was not fully identified as examined by experiment. In order to disclose the structure of compound 1, we proposed several possible compounds and calculated each compound, using the following methods. Hartree–Fock with the 3-21G(d) basis set was used for energy calculation and geometry optimizations of those compounds. Excitation energies were obtained from time-dependent density functional theory (TD-DFT) using the B3LYP functional with the 3-21G(d) basis set. As a result, [(box)(boxH)Li]₂ was found to be one of the possible compounds which had the most stable geometry structure. Its optical properties showed remarkably good agreement with the characterization data of compound 1. In addition, the structure of [(box)(boxH)Li]₂ was also compared well with that of LiBq₄ which was reported by the groups of Tao and was argumentatively asserted by Radu and coworkers [J. Am. Chem. Soc. 125 (2003) 880].     

Shift between emission and absorption lines at natural strong narrowing of Mössbauer lines. Way to the exclusion of systematic errors in experiments with natural strong narrowing

The natural strong narrowing of Mössbauer lines on long-lived isomers, which was correctly detected in [Yu. D. Bayukov, A. V. Davydov, Yu. N. Isaev, G. R. Kartashov, M. M. Korotkov, and V. V. Migachev, JETP Lett. 90, 499 (2009)] and consistently explained in [S.V. Karyagin, JETP Lett. 98, 174 (2013)] is additionally studied. It is shown that the chemical shift δ between γ emission and absorption lines appears in experiments with natural strong narrowing in the homogeneous medium of a γ source. This shift was previously thought to be impossible. The theory of the γ-resonance gravitational spectrum is developed with allowance for the shift δ. The shift δ and new linewidth k including this shift are determined; this new linewidth is noticeably smaller than that without the shift δ. It is shown that the lifetimes of isomers in experiments with natural strong narrowing are strongly limited from above by the suppression of the γ resonance by the shift δ. The smallness of δ confirms the recently revealed effect of strong natural suppression of monopole broadening [S. V. Karyagin, JETP Lett. 103, 213 (2016)]. It is shown that the electron density on the Ag nucleus inside grains is lower than that at their periphery by ~10^-14%. To detect thinner effects, experiments of a new type are proposed to exclude systematic errors.     

Bound and unbound rovibrational states of the methane-argon dimer

ABSTRACT

Peculiarities of the intermolecular rovibrational quantum dynamics of the methane-argon complex are studied using a new, ab initio potential energy surface [Y.N. Kalugina, S.E. Lokshtanov, V.N. Cherepanov, and A.A. Vigasin, J. Chem. Phys. 144, 054304 (2016)], variational rovibrational computations, and detailed symmetry considerations within the molecular symmetry group of this floppy complex as well as within the point groups corresponding to the local minimum structures. The computed (ro)vibrational states up to and beyond the dissociation asymptote are characterised using two limiting models: the rigidly rotating molecule's model and the coupled-rotor model of the rigidly rotating methane and an argon atom orbiting around it.     

On the Li Coefficients for the Hecke L-functions

In this paper, we compute and verify the positivity of the Li coefficients for the Hecke L-functions using an arithmetic formula established in Omar and Mazhouda, J. Number Theory 125(1), 50–58 (2007) and J. Number Theory 130(4), 1098–1108 (2010) and the Serre trace formula. Additional results are presented, including new formulas for the Li coefficients and a formulation of a criterion for the partial Riemann hypothesis. Basing on the numerical computations made below, we conjecture that these coefficients are increasing in n.     

Transparent Boundary Conditions for Split-Step Padé Approximations of the One-Way Helmholtz Equation

In this paper, we generalize the nonlocal discrete transparent boundary condition introduced by F. Schmidt and P. Deuflhard (1995, Comput. Math. Appl.29, 53–76) and by F. Schmidt and D. Yevick (1997, J. Comput. Phys.134, 96–107) to propagation methods based on arbitrary Padé approximations of the two-dimensional one-way Helmholtz equation. Our approach leads to a recursive formula for the coefficients appearing in the nonlocal condition, which then yields an unconditionally stable propagation method.     

IDENTIFICATION OF DAMPING: PART 4, ERROR ANALYSIS

In previous papers (S. ADHIKARI and J. WOODHOUSE 2001 Journal of Sound and Vibration243, 43-61; 63-88; S. ADHIKARI and J. WOODHOUSE 2002 Journal of Sound and Vibration251, 477-490) methods were proposed to obtain the coefficient matrix for a viscous damping model or a non-viscous damping model with an exponential relaxation function, from measured complex natural frequencies and modes. In all these works, it has been assumed that exact complex natural frequencies and complex modes are known. In reality, this will not be the case. The purpose of this paper is to analyze the sensitivity of the identified damping matrices to measurement errors. By using numerical and analytical studies it is shown that the proposed methods can indeed be expected to give useful results from moderately noisy data provided a correct damping model is selected for fitting. Indications are also given of what level of noise in the measured modal properties is needed to mask the true physical behaviour.     

Current short-range tests of the gravitational inverse square law

Motivated in large part by the possibility of observing signatures of compact extra dimensions, experimental searches for deviations from Newtonian gravity at short distances have improved in sensitivity by many orders of magnitude in the past five years. We review the essential features of the experiments responsible for the current limits on new effects in the range from a few microns to a few centimeters, and discuss prospects for the near future. To cite this article: J.C. Long, J.C. Price, C. R. Physique 4 (2003).     

Optimization of the Water-PRESS Pulse Sequence and Its Integration into Pulse Sequences for Studying Biological Macromolecules

In this paper, the recently developed “Water-PRESS” method of water suppression [W. S. Price and Y. Arata (1996),J. Magn. Reson. B112,190] in which homospoil pulses are used to manipulate the effects of radiation damping on the water resonance and thereby selectively alter the effective relaxation times of the water resonance with respect to the solute (e.g., biological macromolecules) resonances is further developed and applied. In the present work, methods for optimization in terms of degree of water suppression and in temporal terms (important for the application of Water-PRESS to multidimensional experiments) are considered so that recycle delays of less than 2.3 s (including the acquisition time) are possible. Also, a simple modification which allows the observation of solute resonances with relaxation times similar to that of the water resonance is presented. Finally, the inclusion into more complicated pulse sequences is also discussed. Experimental examples using aqueous samples of lysozyme and immunoglobulin are given. Compared to most other NMR water suppression techniques, this method is extremely simple to implement and optimize and does not require accurately calibrated RF pulses or perfect lineshape.     

Comment on “Concrete Representation and Separability Criteria for Symmetric Quantum State”

Recently, Li et al. (Int. J. Theor. Phys. 53(9), 2923–2930 (2014)) presented the concrete representation of density matrix of symmetric quantum states . Moreover , according to this concrete representation of the density matrix for symmetric quantum states, Li et al. (Int. J. Theor. Phys. 53(9), 2923–2930 (2014)) have established Theorem 4.1. In this Comment, we would like to point out that Theorem 4.1 given by Li et al. (Int. J. Theor. Phys. 53(9), 2923–2930 (2014)) is incorrect in general.     

Absorption Measurements of Ar–COb-Type Rotational Transitions with a Supersonic Jet Millimeter-Wave Spectrometer

Pure rotationalb-type transitions of Ar–CO were observed in the frequency range from 70 to 103 GHz using a combination of millimeter-wave absorption spectroscopy with supersonic jet expansion. The millimeter-wave radiation was generated by precision tunable synthesizers equipped with backward wave oscillators. Altogether 14 transitions belonging toQandRbranches withK_a= 1 − 0 have been measured with an accuracy of about 50 kHz. Our results confirm the microwave–millimeter-wave double resonance experiments of Jäger and Gerry [J. Chem. Phys.102,3587–3592 (1995)] and demonstrate the sensitivity of the direct absorption technique for the detection of van der Waals clusters with a small dipole moment.     

Investigation of the substituent specific cross‐interaction effects on 13C NMR of the CN bridging group in substituted benzylidene anilines

The substituent effect on ¹³C NMR of the C?N in benzylidene anilines XPhCH?NPhY was investigated, in which the substituents X and Y are in p‐position or in m‐position of the two aromatic rings. The substituent effects including the inductive effects of X and Y, the conjugative effects of X and Y, and the substituent specific cross‐interaction effect were put into one model to quantify the ¹³C NMR chemical shift δ_C(C?N) of the C?N in XPhCH?NPhY. A penta‐parameter correlation equation with correlation coefficient 0.9975 and standard error 0.17 ppm was obtained for 80 samples of compounds. The result shows that the substituents X and Y have an opposite effect on the δ_C(C?N). The electron‐withdrawing effects of X decrease the δ_C(C?N); while the electron‐donating effects of X increase the δ_C(C?N). In contrast, the electron‐withdrawing effects of Y increase the δ_C(C?N); while the electron‐donating effects of Y decrease the δ_C(C?N). A new substituent specific cross‐interaction effect parameter Δσ² was proposed, which indicates that the most substituent specific cross‐interaction effect exists in the pair of max electron‐withdrawing group (EWG) and max electron‐donating group (EDG) or the pair of max EDG and max EWG. Further to verify the obtained correlation equation, 15 samples of model compounds were prepared and their δ_C(C?N) was measured in this work. The predicted δ_C(C?N) values with the obtained equation are in good agreement with the measured ones for these prepared compounds, which confirmed the reliability of the obtained equation. Copyright © 2010 John Wiley & Sons, Ltd.     

A Three-Component Model for Magnetization Transfer. Solution by Projection-Operator Technique,and Application to Cartilage

A projection-operator technique is applied to a general three-component model for magnetization transfer, extending our previous two-component model [R. S. Adler and H. N. Yeung,J. Magn. Reson. A104,321 (1993), and H. N. Yeung, R. S. Adler, and S. D. Swanson,J. Magn. Reson. A106,37 (1994)]. The PO technique provides an elegant means of deriving a simple, effective rate equation in which there is natural separation of relaxation and source terms and allows incorporation of Redfield–Provotorov theory without any additional assumptions or restrictive conditions. The PO technique is extended to incorporate more general, multicomponent models. The three-component model is used to fit experimental data from samples of human hyaline cartilage and fibrocartilage. The fits of the three-component model are compared to the fits of the two-component model.     

Accurate Measurement of Small Spin–Spin Couplings in Partially Aligned Molecules Using a Novel J-Mismatch Compensated Spin-State-Selection Filter

The accurate measurement of small spin–spin coupling constants in macromolecules dissolved in a liquid crystalline phase is important in the context of molecular structure investigation by modern liquid state NMR. A new spin-state-selection filter, DIPSAP, is presented with significantly reduced sensitivity to J-mismatch of the filter delays compared to previously proposed pulse sequences. DIPSAP presents an attractive new approach for the accurate measurement of small spin–spin coupling constants in molecules dissolved in anisotropic solution. Application to the measurement of ¹⁵N–¹³C′ and ¹H^N–¹³C′ coupling constants in the peptide planes of ¹³C, ¹⁵N labeled proteins demonstrates the high accuracy obtained by a DIPSAP-based experiment.