Volume 61, Issue 7-8

In this paper, by means of the general projective Riccati equation method (PREM), the variable separation solutions of the (2+1)-dimensional modified dispersive water-wave system are obtained. By further studying, we find that these variable separation solutions, which seem independent, actually depend on each other. Based on the special variable separation solution and choosing suitable functions p and q, soliton fusion and fission phenomena among peakons, compactons, dromions and semifoldons are firstly investigated. - PACS numbers: 05.45.Yv, 02.30.Jr, 02.03Ik

The contribution of the higher-order correction to nonlinear dust-acoustic waves are studied using the reductive perturbation method in an unmagnetized collisionless mesospheric dusty plasma. A Korteweg - de Vries (KdV) equation that contains the lowest-order nonlinearity and dispersion is derived from the lowest order of perturbation, and a linear inhomogeneous (KdV-type) equation that accounts for the higher-order nonlinearity and dispersion is obtained. A stationary solution is achived via renormalization method

The non-thermal and dust charge effects on a surface electrostatic ion plasma wave are investigated in a semi-bound magnetized dusty Lorentzian plasma. The results show that the phase velocity of the surface wave with negatively charged dust grains is greater than that with positively charged dust grains or that with neutral dust grains. It is also found that the phase velocity increases with increasing the spectral index of the plasma. For the long wavelength domain, however, the phase velocity of the surface wave is found to be almost independent of the spectral index.

The dynamic screening effects on elastic electron-ion collisions are investigated in nonideal plasmas. The second-order eikonal method with the impact parameter analysis is employed to obtain the eikonal phase as a function of the impact parameter, collision energy, thermal energy, and Debye length. The result shows that the eikonal phase decreases with increasing the thermal energy. It is also found that the dynamic screening effects on the eikonal phase are more significant for large impact parameters. The total eikonal cross section is also found to be decreased with increasing the thermal energy. It is important to note that the eikonal cross section and the eikonal phase including the dynamic screening effects are found to be greater than those including the static screening effects.

Linear stability analysis is performed for the onset of thermosolutal convection in a horizontal fluid layer with rigid-rigid boundaries. The temperature field between the walls of the fluid layer consists of two parts: a steady part and a time-dependent periodic part that oscillates with time. Only infinitesimal disturbances are considered. The effect of temperature modulation on the onset of thermosolutal convection has been studied using the Galerkin method and Floquet theory. The critical Rayleigh number is calculated as a function of frequency and amplitude of modulation, Prandtl number, diffusivity ratio and solute Rayleigh number. Stabilizing and destabilizing effects of modulation on the onset of double diffusive convection have been obtained. The effects of the diffusivity ratio and solute Rayleigh number on the stability of the system are also discussed.

Within series of isomeric benzenoid hydrocarbons there is a very good linear correlation between the topological resonance energy (TRE) and the total π-electron energy (Eπ ). Furthermore, the slope of the TRE vs. Eπ regression line is almost independent of the benzenoid isomers considered, and (for all sets of isomers) is nearly equal to 0.5. This implies that comparison of benzenoid isomers with regard to their aromaticity can be made, with equal success, by using both TRE and Eπ . However, Eπ is computed significantly simpler than TRE, and thus advantage should be given to the former. Correlations between TRE and Eπ exist also in the case of non-benzenoid isomers (both alternant and non-alternant), but are of much inferior quality.

High resolution Fourier spectrometry techniques have been used to study the A 1 Σ + u state, which is perturbed by the b 3 Π u state of the Na 2 molecule. This study was achieved by means of exciting the B 1 Π u state from the X 1 Σ + g ground state by 4880 Å and 4965 Å lines of an Ar + laser. The excitation is followed by collisional transfer energy produced between B 1 Π u and (2) 1 Σ + g states ν, which led to the population of the vibrational levels of the (2) 1 Σ + g state v. The analysis of the collision-induced system (2) 1 Σ + g −A 1 Σ + g enabled us to study, in detail, the perturbations of 11 vibrational levels from v = 0 to v = 10 of the A 1 Σ + u state.

In the investigation of the optical and magnetic properties of 3d N ion impurities in semiconductors, the contribution of the covalence must be considered. A modified d function (d ∗ ) and two covalent factors associated with the t 2 and e orbitals have been adopted for describing this covalence. We present the contribution of the covalent factors to the energy matrix of the d ∗7 electron and d ∗3 hole system. This suggests that the d N electron system cannot be explained with the d 10−N hole system when the covalence is considered. The calculation of the energy levels by the d ∗7 energy matrix agrees with the experimental finding of ZnSe:Co 2+ . - PACS numbers: 71.70.Ch, 71.55.Gs

In this paper we report on electron momentum densities in ZnSe using Compton scattering technique. For the directional measurements we have employed a newly developed 100 mCi 241 Am Compton spectrometer which is based on a small disc source with shortest geometry. For the theoretical calculations we have employed a self-consistent Hartree-Fock linear combination of atomic orbitals (HF-LCAO) approach. It is seen that the anisotropy in the measured Compton profiles is well reproduced by our HF-LCAOcalculation and the other available pseudopotential data. The anisotropy in the Compton profiles is explained in terms of energy bands and bond length. - PACS numbers: 13.60.Fz, 78.70. Ck, 78.70.-g

By diagonalizing the complete energy matrix of a d 4 configuration ion in tetragonal symmetry, the zero-field-splitting parameters a, D and F of InP:Cr 2+ have been studied. The local structure distortion parameters ΔR = 0.08 Å and Δθ = 1.01 ◦ were estimated. They show an expansion distortion around Cr 2+ in the InP semiconductor. The Jahn-Teller energy E JT is found to be about 413 cm −1 , which agrees well with the experiment. - PACS numbers: 75.10.Dg; 76.30.-v

CaHPO 4 was obtained by slow evaporation at room temperature. Seven samples, obtained at different annealing temperatures, were characterized by X-ray diffraction and 31 P MAS-NMR spectroscopy. All NMR spectra were analyzed using a DMFIT program. At room temperature, the observed 31 P NMR chemical shifts for the title compound were −1.59, −0.36 and 1.26 ppm with the relative intensities 39%, 10% and 51%, revealing the presence of three non-equivalent phosphorus sites in the structure. The investigation of the NMR tensor shift of all spectra shows that the abounding HPO 2− 4 anion was progressively transformed into P 2 O 4− 7 when the temperature increased

A density functional study was carried out to investigate the C-H···O hydrogen bonding effects on the 17 O electric field gradient and chemical shielding tensors in crystalline 1-methyluracil. Since the structural coordinates were obtained from a neutron diffraction study, no geometry optimization was needed in performing the calculations. It is demonstrated that C-H···O hydrogen bonding has different influences on O2 and O4 EFG and CS tensors. In the tetramer model of 1-methyluracil, which is much closer to the real crystalline phase, the influence of C-H···O on the O4 EFG and CS tensors is significant, whereas this influence is negligible for O2.

Part of the molten system NaF-AlF 3 -Al 2 O 3 was studied by surface tension measurements, which were performed at cryolite ratios (CR) between 1.5 and 3 [CR = n(NaF)/n(AlF 3 )]. The maximal bubble pressure method was applied. The surface adsorption of alumina (Al 2 O 3 ) was also calculated. The obtained results were discussed in terms of the anionic composition of the melt. The addition of AlF 3 to melt with CR= 3 decreases the surface tension, as AlF 3 is surface-active in molten Na 3 AlF 6 . The concentration dependence of the surface tension and the surface adsorption of alumina in the title system are influenced by the formation of surface-active oxofluoroaluminates. An increase of the difference between the surface tension of NaF-AlF 3 mixtures and the surface tension of pure alumina was observed with decreasing cryolite ratio.

The IR spectra of 1,3-diaminopropane adsorbed on NaA (type 4A), CaA (type 5A), NaX (type 13X) and NaY zeolites are reported. From the IR spectral data it can easily be stated that the characteristic NH vibration bands of aliphatic amine groups play an important role in the adsorptions of 1,3-diaminopropane on the mentioned zeolites.

Nanosensors are gaining increasing attention due to the need to detect and measure chemical and physical properties in difficult to reach biological and industrial systems that are in the nano-scale region. This conceptual review surveys various nanosensors, which are categorized into three broad types: optical, electromagnetic and mechanical nanosensors. The sensing concepts and their corresponding advantages are discussed with reference to their applications.

Natural sepiolite minerals and their γ -irradiated forms were investigated by electron paramagnetic resonance (EPR) at room temperature and at 113 K. The EPR signals in powders of natural sepiolite were observed due to clusters of Fe 3+ ions. The paramagnetic centers produced by γ - irradiation of natural sepiolite minerals were attributed to the ĊH 3 at room temperature and ṠO − 2 and ṠO − 3 radicals at 113 K. These centers were found to be perfectly observable above 20 mW microwave power. The g values of all paramagnetic centers have been measured and the A values of some of them have been reported. The results were consistent with the literature data for similar paramagnetic centers.

A corollary to an experimental proposal made by Anton Zeilinger - the famous double-double slit experiment - is suggested to be possible. The double Mach-Zehnder experiment.