Table of contents

August 2015 marks the 70th anniversary of the atomic bombings of Hiroshima and Nagasaki. These bombs, the products of the United States Army's Manhattan Project, helped to end World War II and had enormous long-term effects on global political strategies by setting the stage for the Cold War and nuclear proliferation. This article explores the context and legacy of the Manhattan Project. The state of the war in the summer of 1945 is described, as are how the target cities came to be chosen, deliberations surrounding whether the bombs should be used directly or demonstrated first, and the long-term effects of the Project on individual scientists, the relationship between scientists and society, the subsequent development of nuclear arsenals around the world, and the current status of these arsenals and how they might evolve in the future.

A number of topics, ranging from morphology of aperiodic crystals to indexed enclosing forms of axial-symmetric proteins, nucleic acids and viruses, have been selected among those investigated by the authors in 50 years of research. The basic symmetries involved in fields like superspace, molecular and scale crystallography, are considered from a personal point of view in their time evolution. A number of specific subjects follow, chosen among a few highlights and presented according to the experience of the authors: snow crystals, calaverite ${\mathrm{AuTe}}_{2}$, the incommensurately modulated crystals ${\mathrm{Rb}}_{2}{\mathrm{ZnBr}}_{4}$, ${[{{\rm N}}{({\mathrm{CH}}_{3})}_{4}]}_{2}{\mathrm{ZnCl}}_{4}$ and the mitochondrial ferritin.

This paper examines neutrino flavor evolution outside a supernova neutrinosphere using a one-dimensional model that retains the nonlinear nature of neutrino–neutrino interactions as well as some aspects of the full geometry. In some limiting cases analytic results can be obtained that display different behavior from their counterparts in (linear) solar neutrino flavor evolution. For more general cases, numerical solutions require extended numerical algorithms to achieve stable solutions, and these solutions exhibit standard chaotic behavior.

Dark states were first observed in optical pumping experiments and interpreted as a quenching of fluorescence due to a destructive interference between two absorption amplitudes connecting two ground state sublevels g₁ and g₂ to an excited sublevel e. The atom can absorb light from g₁ and jump to e. Similarly, it can absorb light from g₂ and jump to e. But, if it is in a certain linear superposition of g₁ and g₂, ${c}_{1}{g}_{1}+{c}_{2}{g}_{2}$, the two absorption amplitudes from g₁ to e and from g₂ to e interfere destructively and cancel out. The fluorescence stops. The state ${c}_{1}{g}_{1}+{c}_{2}{g}_{2}$ from which light cannot be absorbed is called a dark state. This paper will start with a description of the first experiments demonstrating the existence of dark states and of the first theoretical interpretations that have been proposed. Dark states appeared to play an essential role in several new physical effects, such as electromagnetically induced transparency, slow light, stimulated Raman adiabatic passage (STIRAP), which will be briefly described. A special emphasis will be given to the applications of dark states in the field of ultracold atoms and molecules. It will be first shown how the use of velocity dependent dark states allows atoms to be cooled below the so-called recoil limit, corresponding to a velocity dispersion of the cooled atoms smaller than the recoil momentum communicated to the atom by the absorption of a single photon. It turned out that a quantitative interpretation of this subrecoil cooling may be given in terms of anomalous random walks and Lévy statistics. Finally, recent applications of dark states to the production of ultracold molecules will be described: production of ultracold polar molecules by the combination of Feshbach resonances and STIRAP; dark states in the photo-association of ultracold atoms allowing a precise determination of the scattering length describing their collisions.

This article provides a brief overview of some of the theoretical aspects of R-parity violation (RPV) in the minimal supersymmetric standard model and its extensions. Both spontaneous and explicit RPV models are discussed and some consequences are outlined. In particular, it is emphasized that the simplest supersymmetric theories based on local $B-L$ predict that R-parity must be a broken symmetry, a fact which makes a compelling case for taking R-parity breaking seriously in discussions of supersymmetry phenomenology.

We study Einstein's equations with a localized plane-symmetric source, with close attention to gauge freedom/fixing and to listing all physically distinct solutions. In the vacuum regions there are only two qualitatively different solutions, one curved and one flat; in addition, on each of the two sides there is a free parameter describing how the slab is embedded into the vacuum region. Surprisingly, for a generic slab source the solution must be curved on one side and flat on the other. We treat infinitely thin slabs in full detail and indicate how thick slabs can increase the variety of external geometry pairs. Positive energy density seems to force external geometries with curvature singularities at some distance from the slab; we speculate that such singularities occur in regions where the solution cannot be physically relevant anyway.

Hugh Everett thought it was preposterous to accept the Schrödinger equation as a fundamental law of quantum physics, but then assert that it is usually violated in any observation of quantum phenomena. Demanding that the Schrödinger equation always holds led him to the 'many worlds' interpretation. To avoid this conclusion, I propose that the Schrödinger equation is not fundamental, but that one should instead regard as primary a von Neumann version of the equation which lets the density matric evolve unitarily, but where conclusions reached concerning measurements always involve the non-unitary step of tracing out environmental degrees of freedom which always exist even if the system in question is the entire observable universe.

Topics in supersymmetry and superstring phenomenology are discussed, with emphasis on the weakly coupled heterotic string.

Recent spacecraft observations in the solar wind and in the Earth's magnetosheath indicate that the dissipation range of magnetic turbulence probably takes place at electron scales. Here, we derive nonlinear electron magnetohydrodynamic (EMHD) equations for warm plasma, i.e. with the ratio of thermodynamic and magnetic pressures, $\beta \sim 1$. This model describes plasma turbulence under the solar wind and magnetosheath conditions on the electron spatial scales and with the characteristic frequency that does not exceed the electron gyrofrequency. We show that at electron scales and in the presence of a sufficiently large temperature anisotropy ${T}_{{e}_{\perp }}/{T}_{{e}_{\parallel }}\gt 1$, there exist self-organized, coherent, nonlinear dipole vortex structures associated with obliquely propagating whistler waves. These can be visualized as pairs of counterstreaming helicoidal currents that produce both the compressional and torsional perturbations of the magnetic field. In contrast to the previously known long-range EMHD dipolar vortices in a cold plasma, this novel solution is an evanescent mode, strongly localized in space (with wave numbers ${k}_{\perp }\gg {k}_{\parallel }$). It can constitute a building block for the plasma turbulence at short scales and provide a possible scenario of turbulence dissipation at electron scales.

Generation of quasi-static magnetic fields, due to the Weibel instability is studied in a relativistic quantum plasma. This instability is induced by a temperature anisotropy. The dispersion relation and growth rates for low frequency electromagnetic perturbations are derived using a wave-kinetic equation which describes the evolution of the electron Wigner quasi-distribution. The influence of parallel kinetic effects is discussed in detail.

A new transverse mode in a two-stream magnetized quantum plasma is studied by means of a quantum hydrodynamic model, under non-relativistic and ideal Fermi gas assumptions. It is found that Fermi pressure effects induce a minimum cutoff wavelength for instability, unlike the classical case which is unstable for larger wavenumbers. The external magnetic field is also shown to produce a stabilizing effect. Conditions for the applicability of the model and specific parameters for experimental observations are thoroughly discussed.

The difference between simple drift waves driven by the density gradient and thermal instabilities driven by the temperature gradient is discussed. It is shown that thermal instabilities basically are of a kinetic nature although they can also be accurately described by an advanced fluid model.

The three-dimensional far-field electrostatic potential of two co-moving point charges are considered. In contrast to the one-dimensional nonlinear case, it is found that the shielding behavior remains similar to that of a single moving charge.

The basic features of obliquely propagating dust-acoustic (DA) solitary waves (SWs) in a three-component magnetized dusty plasma (containing inertial negatively as well as positively charged dust grains, and nonextensive ions) have been theoretically investigated. The reductive perturbation technique is employed in order to derive the Korteweg–de Vries (K–dV) equation. The stationary solitary wave solution of the K–dV equation, which describes the characteristics of SWs associated with ultra-low-frequency, long wavelength DA waves, is obtained and numerically analyzed. It is observed that the basic characteristics (polarity, amplitude, width, speed, etc) of the DA SWs are significantly modified by the effects of ion nonextensivity, external magnetic field, and angle between the directions of external magnetic field and wave propagation. The findings of this investigation may be used in understanding the wave propagation in space and laboratory plasmas in which dust of opposite polarity coexists.

Propagation of microwaves along the transmission line with smoothly continuously distributed capacitance and inductance (gradient transmission line) is considered in the framework of an exactly solvable model. The appearance of strong heterogeneity-induced plasma-like dispersion in gradient transmission line determined by the sizes and shapes of these distributions, is visualized by means of this model. Owing to this dispersion the energy transport in the line discussed can be ensured by both travelling and evanescent microwave modes, characterized by the real and imaginary wave numbers, respectively. The reflectance spectra for microwaves, incident on this heterogeneous transition section located between two homogeneous sections of transmission line are presented, the antireflection properties of this section are demonstrated. The interference of evanescent and anti-evanescent microwave modes is shown to provide the effective weakly attenuated energy transfer in the tunneling regime. The analogy between this microwave system and gradient nano-optical photonic barrier in revealed.

The properties of a particular Misner–Thorne wormhole (WH) are investigated. The 'exotic stress–energy' needed to maintain the WH open corresponds to a massless scalar field whose Lagrangean density contains a negative kinetic term. While the Komar energy of the spacetime is vanishing due to the negative energy density and radial pressure, the ADM energy is (minus) the Planck energy. The timelike geodesics are hyperbolae and any static observer is inertial. The null radial trajectories are also hyperbolae and Lorentz invariant as Coleman–de Luccia expanding bubble or Ipser–Sikivie domain wall. Using a different equation of state for the fluid on the dynamic WH throat of Redmount and Suen, we reached an equation of motion for the throat (a hyperbola) that leads to a negative surface energy density and the throat expands with the same acceleration $2\pi | \sigma |$ as the Ipser–Sikivie domain wall.

In this paper, the stability and stochastic resonance (SR) phenomenon induced by the multiplicative periodic signal for a metapopulation system driven by the additive Gaussian noise, multiplicative non-Gaussian noise and noise correlation time is investigated. By using the fast descent method, unified colored noise approximation and McNamara and Wiesenfeld's SR theory, the analytical expressions of the stationary probability distribution function and signal-to-noise ratio (SNR) are derived in the adiabatic limit. Via numerical calculations, each effect of the addictive noise intensity, the multiplicative noise intensity and the correlation time upon the steady state probability distribution function and the SNR is discussed, respectively. It is shown that multiplicative, additive noises and the departure parameter from the Gaussian noise can all destroy the stability of the population system. However, the noise correlation time can consolidate the stability of the system. On the other hand, the correlation time always plays an important role in motivating the SR and enhancing the SNR. Under different parameter conditions of the system, the multiplicative, additive noises and the departure parameter can not only excite SR phenomenon, but also restrain the SR phenomenon, which demonstrates the complexity of different noises upon the nonlinear system.

Although general relativity allows the existence of closed timelike curves (CTCs), self-consistency problems arise (the 'grandfather paradox' among others). It is known that quantum mechanical consideration of the matter formally removes all the paradoxes, but the questions about causal structure remain. On the other hand, the idea of postselected CTCs (P-CTC) in quantum teleportation has know been put forward and experimentally implemented. We consider these problems with the aid of quantum causal analysis, where causality is defined without invoking the time relation. It implements the Cramer principle of weak causality, which admits time reversal in entangled states. We analyze Deutsch CTCs (D-CTC) with different kinds of interactions between the chronology-violating and chronology-respecting particles, with refined inferences about mixedness, quantum/classical correlations, entanglement and thermodynamics in the D-CTC. The main result is that time reversal causality can really exist, however, the final quantum state does not place retrospective constraints on the initial state, instead the final state can influence the state inside the D-CTC. This is effectively the implementation of Novikov self-consistency principle. The P-CTC has radically different properties; in particular, if the initial state was pure, the final state is always pure too. Self-consistency is controlled by the initial state-dependent traversability of the P-CTC.

Recently, two-mode entangled squeezed states have been produced using even and odd squeezed states. Based on such entangled states, we introduce two new classes of quantum states, namely single-mode excited (depleted) entangled squeezed states which are obtained via the iterated action of the creation (annihilation) operator on the first mode of the two-mode entangled squeezed states. In continuation, we study the amount of entanglement of the introduced states by calculating the 'concurrence' and 'linear entropy'. In addition, we investigate several nonclassicality features such as the sub-Poissonian statistics, second-order correlation function between the two modes and quadrature squeezing. Finally, in order to establish the physical realization of the introduced states, a theoretical scheme for their generation based on the interaction of a two-level atom with a quantized cavity field is proposed.

We study two superconducting charge qubits sharing a large Josephson junction with transient effects considered for the case of the linear sweep model to explore the influence of a time-varying field on the entanglement of the qubits. We show that the fluctuations in the entanglement can be controlled by the transient effects. Moreover, the time-averaged entanglement oscillates smoothly and then fluctuates with the increasing influence of the transient effects.

In the present paper, the steady-state properties of a time-delayed cancer growth system that is driven by a correlated multiplicative noise and an additive one are investigated. The numerical results show that the conventional stochastic resonance (SR) phenomenon occurs in the tumor cell growth model for different system parameter values. The results indicate that the additive noise strength always weakens the SR phenomenon, while the time delay mainly increases the SR phenomenon. On the other hand, it is shown that the effects of the strength of the multiplicative noise are different.

We give two conditionally exactly solvable inverse power law potentials whose linearly independent solutions include a sum of two confluent hypergeometric functions. We notice that they are partner potentials and multiplicative shape invariant. The method used to find the solutions works with the two Schrödinger equations of the partner potentials. Furthermore, we study some of the properties of these potentials.

The nonlinear dynamics of resistive flow with a chemical reaction is studied. Proceeding from the Lagrangian description, the influence of a chemical reaction on the development of fluid singularities is considered.

With the aid of the gauge transformation between the corresponding 3 × 3 matrix spectral problem, Darboux transformation for the coupled modified Korteweg–de Vries (cmKdV) equation is derived. Depending on the Darboux transformation, explicit solutions for this equation are given and some figures are plotted. Finally, infinitely many conservation laws of the cmKdV equation are constructed.

Trying to generate a chaotic signal on a computer (or a finite precision machine) will lead to dynamical degradation of chaotic properties. In this paper, we use a variable function to replace the input variable of the chaotic system, which does not change the original chaos equation. We show that our new system has the properties of sensitive dependence on initial conditions and transitivity, and when the system is running on the finite precision device, the dynamical degradation has been greatly improved compared to the original digital chaotic system. Our method is universal, can be easily used in all the digital chaotic systems and is more efficient than the other frequently used methods in the overall characteristics.

The Blume-Caple model on the triangular lattice is considered in this paper. Using the (perturbative) real-space renormalization group (RSRG) technique we analytically obtain the running of the parameters of the model, i.e., the exchange integral J and the crystal field Δ. The observations show that the first-order calculations are insufficient to capture the tricritical phenomena, and the RG analysis based on second-order expansion of the partition function show qualitative agreement with the previous works. This reveals that the second-order perturbation works appropriately, to obtain the qualitative features of the phase diagram of the model, e.g., a tricritical point which is unstable towards the Ising critical point from one side (which forms the line of second order, separating the ferromagnetic and paramagnetic phases) and the critical point at $T\to 0$ and $\Delta =3J$ from the other side (which forms the line of first-order transition separating ferromagnetic and zero state phases). This analysis shows also that there is another unstable critical point at $({\Delta }_{{CP}1},J=0)$, with the RG eigenvalue ${\Lambda }_{\Delta }\simeq 1.014(6)$ in the Δ-direction (towards S = 0 zero state and $S=\frac{1}{2}$ paramagnetic phases).

Effective Schrödinger equations, governing the mean movement of a system influenced by fast oscillating external perturbation, are derived. The method represents a direct and straightforward quantum extension of the Kapitza's approach provided in the Schrödinger picture. First-order terms (over inverse frequency of external driving) in effective Hamiltonians that cannot be eliminated by a unitary transformation, have been derived. Additional terms, in comparison with a standard equation, are similar to those found in the classical case and they may be responsible for a variety of new interesting effects.

In this paper, we consider a method for the simple exact analytical solution of autonomous nonlinear oscillator equations. While the approach can be used to solve nonlinear oscillator equations with smooth solutions (and we demonstrate this with an application of the approach to an autonomous Duffing equation), our primary interest will be on solving equations with non-smooth yet continuous solutions. To this end, we consider the second-order pseudo-oscillator equation ${yy}\prime\prime +1=0$ used as a simple model of the path taken by an electron in an electron beam injected into a plasma tube. In recent results of Gadella and Lara, the authors claim the non-existence of periodic solutions to this equation, but actually show that there are no smooth periodic solutions. We show that although there are no smooth solutions to this equation, there does exist a type of continuous periodic solution on the whole problem domain, hence periodic solutions do indeed exist. These periodic solutions can be constructed to have any arbitrary positive period, and the amplitude of these solutions increases as the period is increased. The approach allows one to construct periodic solutions to a variety of nonlinear oscillator equations, even if the solutions are not smooth, and hence could be a useful tool for those interested in physical applications in which nonlinear oscillator models arise.

The data collected with a radioactively pure ZnWO₄ crystal scintillator (699 g) in low background measurements during 2130 h at the underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (INFN, Italy) were used to set a limit on possible concentration of superheavy eka-W (seaborgium Sg, Z = 106) in the crystal. Assuming that one of the daughters in a chain of decays of the initial Sg nucleus decays with emission of high energy α particle (${{Q}_{\alpha }}\gt 8$ MeV) and analyzing the high energy part of the measured α spectrum, the limit N(Sg)/N(W) $\lt 5.5\times {{10}^{-14}}$ atoms/atom at 90% C.L. was obtained (for Sg half-life of 10⁹ yr). In addition, a limit on the concentration of eka-Bi was set by analysing the data collected with a large BGO scintillation bolometer in an experiment performed by another group (Cardani et al 2012 JINST 7 P10022): N(eka-Bi)/N(Bi) $\lt 1.1\times {{10}^{-13}}$ atoms/atom with 90% C.L. Both the limits are comparable with those obtained in recent experiments which instead look for spontaneous fission of superheavy elements or use the accelerator mass spectrometry.

The present study introduces an optical as well as image processing method that is effective in the study of PM-355 solid state nuclear track detector (SSNTDs) irradiated with α-particles at different times. Laser light with Gaussian extent and 635 nm wavelength is used to accomplish this goal. An imaging processing technique is utilized for the study of the nature and characteristics of a transmitted laser beam through PM-355 SSNTDs. Semi-empirical formulas are obtained which can be used as guide lines to calculate unknown dose. The present method is effective and simple and demands no sophisticated tool methods.

The proton neutron interacting boson model (IBM-2) has been used to make a systematic study of Strontium isotopes in this mass region of A ∼ 80 with 38 $\leqslant$N$\leqslant$ 48 and Z = 38. The three-term Talmi–Otsuka general Hamiltonian in the framework of the neutron proton version of the Interaction boson model was used to perform the calculations. The yrast levels energy are reproduced. The beta and gamma band energy levels also matched well. The reduced transition probabilities were also calculated and were found to be in agreement with the experimental values. In addition, g-factor for the ${2}_{1}^{+}$ state was evaluated. Possible candidates for mixed symmetry states were also predicted for several nuclei in this isotopic chain.

The structure of multiphonon K = 4 γγ-band of ${}^{112}\mathrm{Ru}$, ${}^{104}\mathrm{Mo}$, ${}^{106}\mathrm{Mo}$ , and ${}^{108}\mathrm{Mo}$ nuclei are investigated using the recently proposed modified soft rotor formula (MSRF). The positive values of the moment of inertia and small values of softness parameter are obtained. The calculated values of moment of inertia of γγ-band are almost equal to the moment of inertia of γ-band, which indeed should be equal to the moment of inertia of ground band. The constant energy parameter EK in the MSRF is also illustrated for K = 4 γγ-band. The staggering pattern in the multiphonon γγ-band is also discussed in detail. The study of one-phonon K = 2 γ-band and two-phonon K = 4 γγ-band using MSRF yields good energy values.

The resonant process of electron–positron pairproduction by an electron in a subcritical magnetic field has been studied when the pair is produced to exited Landau levels. The spin dependency of the process rate has been analyzed. In the spin state with the greatest rate the virtual photon is emitted with a flip of electron spin. This behavior is not suppressed for radiative transitions from a relativistic initial state to low energy levels.

When a two-electron atom or ion is enclosed in an impenetrable spherical cavity, level crossings and avoided crossings are observed as the cavity radius changes. The locations of those crossings depend on the cavity radius and the nuclear charge of the system. The question arises as to whether this crossing behavior is unique to the one-electron Coulomb potential or whether it can be observed in other confined single-particle electron potentials. In this work we examined some low-lying singlet and triplet states of two-electron systems with isotropic harmonic single-particle 3D potentials. The spherically symmetric S states are analyzed using variational energies calculated with Hylleraas-type function. The energy dependence of low-lying states is considered as a function of the cavity radius and the harmonic force constant. For positive force constants, there exist cavity radii where the 2¹S and 1³S states are degenerate. Analogous points do not exist for the two-electron quantum dot where the one-electron potential corresponds to an infinite rectangular box. The structure of the energy spectrum for negative force constants is also studied. The similarities and differences of the two-electron S states for the Coulomb and harmonic potentials are considered.

In this paper the diffusion Monte Carlo method is applied to the confined hydrogen atom with different confinement geometries. This approach is validated using the much studied spherical and cylindrical confinements and then applied to cubical and squared ones, for which data are not available, as new applications of the method relevant to solid state physics. The energy eigenvalues of the ground state and one low-lying excited state are reported as a function of the characteristic confinement length.

We consider a semi-classical model to describe the origin of the spin–orbit interaction in a simple system such as the hydrogen atom. The interaction energy $U$ is calculated in the rest-frame of the nucleus, around which an electron, having linear velocity ${\boldsymbol{v}}$ and magnetic dipole-moment ${\boldsymbol{\mu }},$ travels in a circular orbit. The interaction energy $U$ is due to the coupling of the induced electric dipole ${\mathcal{P}}=({\boldsymbol{v}}/c)\times {\boldsymbol{\mu }}$ with the electric field ${{\boldsymbol{E}}}_{n}$ of the nucleus. Assuming the radius of the electron's orbit remains constant during a spin-flip transition, our model predicts that the energy of the system changes by $\Delta {\mathcal{E}}=\frac{1}{2}U,$ the factor $\frac{1}{2}$ emerging naturally as a consequence of equilibrium and the change of the kinetic energy of the electron. The correct $\frac{1}{2}$ factor for the spin–orbit coupling energy is thus derived without the need to invoke the well-known Thomas precession in the rest-frame of the electron.

Mg-doped zinc oxide (Mg_xZn_1−xO (0 ≤ x ≤ 0.20)) samples were synthesized by polymeric precursor method. The structural and optical properties were investigated by x-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), UV–visible spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopy. XRD patterns reveal that synthesized samples have a wurtzite structure. Lattice parameters, the degree of distortion of the samples were calculated from the XRD. SEM images show that the synthesized samples contain the elongated spherical shaped grains. The Raman scattering investigation and FTIR spectra authenticate the presence of Mg in the system and also show phase segregation at the higher Mg doping concentration. Optical band gap energy is determined from the Tauc relation. It is interesting to know that optical band energy exhibits blue shift with the increase of Mg doping concentration up to 16 mole %.

Kossel diffraction under standing-wave excitation in a one-dimensional photonic crystal is investigated. It is shown that by combining the reciprocity theorem, the Fermi golden rule and the concept of density of photonic modes, it is possible to predict the behavior of the Kossel diffraction in such a system.

We investigate the dispersion properties of surface quantum ion-acoustic wave oscillations on an electron–ion quantum plasma half-space, taking into account the quantum diffraction effects. We deduce the perturbed electron density by using the linearized quantum fluid model, while the ion density perturbation is obtained by the classical theory. We derive an analytical dispersion relation for the surface waves of the system with low-frequency, by applying the Poisson equation as well as the appropriate boundary conditions. We use the dimensionless parameter H, proportional to quantum tunneling effects and show the system support linear quantum ion-acoustic waves, where in the limit of small H, the classical ion-acoustic waves emerge.

In this work, a He atmospheric plasma jet was generated in stable bullet mode by using a dielectric barrier single electrode configuration. The plasma bullets were generated by four different excitation high-voltage waveforms and propagated through a dielectric barrier quartz tube. Corresponding charge, propagation speed and density were evaluated by current monitoring of the bullets, which were flowing through the travelling-bullet tube. It was revealed that positive bullets will be generated with higher current signals, charge, density and propagation speed by an excitation high-voltage waveform having a broader positive width and a greater portion of negative voltage (complex waveform). On the other hand, an excitation high-voltage with negative polarity initiates faster bullets than that of positive polarity. Last but not least, the optical emission spectroscopy results confirmed our electrical diagnostic results, and showed that more active and intense plasma is generated by the waveform with longer positive width and more negative portion.

A novel directly driven target with enhanced radiation is presented in this paper. A spherical hohlraum with laser entrance holes is built to allow lasers to be injected onto the directly driven capsule without intersection. The additional spherical hohlraum can be utilized to absorb a portion of scattering lasers, and generate x-ray to re-radiate the centrally located capsule, in which the laser efficiency and driven symmetry on the capsule are demonstrated to be significantly improved.

Beta-induced Alfvén eigenmodes (BAEs) during strong tearing modes (TMs) have been frequently observed in fast-electron plasmas of EAST tokamak. The dynamics of the short-scale (${k}_{\perp }{\rho }_{s}~\mathrm{1.5-4.3})$ density fluctuations during the activity of BAEs with strong TMs has been preliminarily investigated by a tangential CO₂ laser collective scattering system. The results suggest the active, but different, response of short-scale density fluctuations to the TMs and BAEs. In the low-frequency (0–10 kHz) part of density fluctuations, there are harmonic oscillations totally corresponding to those of TMs. In the medium-high frequency (10–250 kHz) part of density fluctuations, with the appearance of the BAEs, the medium-high frequency density fluctuations begin to be dominated by several quasi-coherent (QC) modes, and the frequencies of the QC modes seem to be related to the changes of both TMs and BAEs. These results would shed some light on the understanding of the multi-scale interaction physics.

In the present work full $1D3V$ particle-in-cell (PIC) simulations have been carried out for the propagation of relativistic electron beams (REBs) through an inhomogeneous background plasma. The suppression of the filamentation instability, responsible for beam divergence, is shown. The simulation also confirms that in the nonlinear regime too the REB propagation is better when it propagates through a plasma whose density is inhomogeneous transverse to the beam. The role of inhomogeneity scale length, its amplitude and the transverse beam temperature etc, in the suppression of the instability is studied in detail.

Dark solitons collision in an ultracold neutral plasma in the framework of the phenomenological generalized hydrodynamic model is reported. The derivative expansion method is used to derive a nonlinear Schrödinger equation for describing the low frequency modulation. The critical wavenumber k_c, which indicates where the modulational instability sets in, is determined precisely. Also, the modulationally stable and unstable regions are obtained for a wide range of the wavenumber k and the ions effective temperature ratio ${\sigma }_{*}$. In the stable regions, the collisions between two-dark solitons are investigated using the extended Poincaré–Lighthill–Kuo method and their corresponding phase shifts are derived. The dependence of both ${\sigma }_{*}$ and k on the phase shift is examined.

Surface tension σ of sub-nanometric bubbles in n-nonadecane + argon system as a function of pressure was estimated using the positron lifetime spectroscopy. The surface tension is higher than for flat surface (due to negative bubble curvature). The coefficient (∂σ/∂p)_p=0 is negative but much smaller than for flat gas-liquid dividing surface. It can be explained by the lack of adsorbed argon layer on the bubble surface. In the narrow range of temperatures, where nonadecane melts by application of argon pressure, the concentration of argon in the liquid is found smaller than at higher temperatures and probably a kind of intermediate structure is formed.

A harmful environmental problem such as cement kiln dust (CKD) was considered as a source of CaO and SiO₂, which are useful oxides for the glass industry. So, Na₂O, B₂O₃, Bi₂O₃, PbO and CKD were used to fabricate new borate based glasses. The structure of the prepared glasses was studied by FTIR before and after gamma irradiation at doses up to 120 kGy. Analysis of FTIR before irradiation revealed that CKD split the characteristic broad band of the vibrations of BO₃ structural units into two bands and created two effective ranges of concentrations which were confirmed by N₄ calculations. After gamma irradiation, the intensity of the FTIR bands decreased and the structure of glass was weakened when 0 ≤ CKD ≤ 23.5 mol% as a result of energy transferred by gamma rays. Increasing CKD beyond this limit created bridging oxygens, more covalent bonds and interlinked the structural groups of the glass network which may resist the irradiation effects. The glass containing 32 mol% of CKD showed higher resistance for radiation effects which was attributed to its strong covalent bonds and to [BiO₆] and [PbO₆] structural units.

First-principles density functional theory calculations were carried out to study the structural, electronic, optical and electrical properties of fluorine-doped zinc oxide in detail. Fluorine substitutions of the oxygen sites create shallow donors derived mainly from the orbital 2p of fluorine. Additionally, the calculated optical properties reveal that the energy band gap gradually expands when increasing the fluorine doping level, which leads to a blue-shift in the optical transparency. More interestingly, the electrical conductivity is significantly enhanced after fluorine doping.

This paper studies excitonic effects in the optical properties of alkaline earth chalcogenides (AECs) by solving the equation of motion of the two-particle Green function, the Bethe–Salpeter equation (BSE). On the basis of quasi-particle states obtained by the GW approximation, (BSE + GW), the solution of BSE improves agreement with experiments. In these compounds, the main excitonic structures were reproduced appropriately. In the optical absorption spectra of AECs, the main excitonic structures originate in the direct transitions at X and Γ symmetry points, as confirmed by the experiments. In addition to real and imaginary parts of the dielectric functions, excitonic effects were studied in the electron energy loss functions of AECs. Moreover, the G₀W₀ approximation was used in order to determine the energy band gaps of AECs. This showed that except for MgO and BaO, the other AECs under study have indirect band gaps from Γ to X.

Self-ordered Co nanowire arrays with different diameters of 30, 70 and 75 nm were grown into the anodized aluminum oxide templates by variation of deposition current between 5 and 55 mA. Increasing diameter of the nanowires enhances interaction between the nanowires, thereby decreasing the coercivity. However, increasing the deposition current decreases coercivity due to increase in deposition of light hydrogen ions. The microstructure investigations by x-ray diffraction patterns revealed that varying the diameter of deposited nanowires at constant current caused variation of preferential crystalline growth of the polycrystalline nanowires. Comparing first-order reversal curve (FORC) diagrams of the samples with different diameters and deposition currents revealed magnetization contribution of each FORC feature is proportional with a certain crystalline direction. Magnetic moment contribution of the domains with low and high coercivity and along the H = 0 axis is correlated with intensity of Co (100), (110), (002) and (101), respectively.

Experimental and numerical results about the propagation of optical signals in a bidirectional two-wave mixing system with Au nanocomposites and carbon nanotubes are presented. Au nanoparticles embedded in a TiO₂ thin solid film were prepared by a sol–gel processing route; while carbon nanotubes were obtained by a thermal decomposition approach. A thin film conformed by carbon nanotubes was put on top of the Au nanocomposites for the nonlinear optical measurements. A two-wave mixing experiment was conducted to distinguish the direction of propagation of a probe-beam through the exploration of an induced birefringence and two-photon absorption. The third-order nonlinear optical response of the sample was evaluated by considering discrete groups of energy numerically modeled by the beam propagation method. Remarkable differences exhibited by the propagation and counter-propagation of a polarized probe beam were identified by nanosecond pulses at 532 nm wavelength. By employing a 405 nm wavelength as a probe beam, we were able to change the behavior of the direction of maximum Kerr transmittance in a particular geometry of a non-degenerated multi-wave system. It can be contemplated that the influence of distinctive near- and off-resonant excitations of the samples seems to be useful to control a selective one-way transmittance with potential applications for developing all-optical systems.

Nd-doped Li–Ti ferrites with compositional formula Li_0.4Ti_0.1Fe_2.5−xNd_xO₄ (where x = 0.0, 0.025, 0.05, 0.075 and 0.10) are prepared at 450 °C by combustion synthesis. X-ray analysis showed the limit of Nd-concentration for formation of single phase cubic is 0.075 and thereafter a secondary phase of FeNdO₃ is observed. As the Nd-concentration increased to 0.075 the lattice parameter increased, which is attributed to the incorporation of larger ionic radius of Nd³⁺ ions in place of smaller ionic radius of Fe³⁺ in the spinel lattice. When Nd-concentration is 0.10, some of the Nd³⁺ ions diffuse to the grain boundaries, which can be correlated from scanning electron microscope analysis. The infrared spectra have shown three strong absorption bands in the range 400–600 cm⁻¹ and confirming the occupancies of Nd³⁺ into the spinel lattice. We explained for n-type semiconductors the Seebeck coefficient should be negative only. Saturation magnetization (M_S) value increases with increase in Nd-concentration indicating that Nd³⁺ ions are replacing the Fe³⁺ ions in the spinel lattice.

We consider the pairing between conduction band electrons, and the valence band holes in the neutral bilayer-type structures. By employing the bilayer Hubbard model, we show the possibility of the inter-plane exciton formation in the system without applied external field. The in-plane and inter-plane Coulomb interaction effects on the pairing mechanism are considered, and the role of the in-plane particle hopping asymmetry on the gap behavior is analyzed in the paper. We show that both Frenkel-type pairing channel and Wannier–Mott-type excitonic pairings are present in the considered system. We analyze also the structure of the chemical potential in the bilayer system. The temperature effects, and the tunable inter-plane electron hopping effects are discussed. For the Frenkel channel, we have shown a particular behavior of the chemical potential at very low temperatures, which is related to the degenerated Frenkel-gap.

Reciprocity principles, which entail equivalent outcome on exchange of cause and effect, are widely used and accepted. We present a piezoelectric composite system designed so that reciprocity does not hold; sensitivity is substantially enhanced. Reciprocity failure is observed in which the piezoelectric direct effect (stress causes polarization) sensitivity ${d}_{{kij}}^{d}$ is unequal to the converse effect (electric field causes deformation) sensitivity ${d}_{{kij}}^{c}$. The piezoelectric polymer PVDF under isothermal conditions on a polymer substrate obeys reciprocity. Reciprocity failure occurs when a bumpy contact condition causes stress gradients. Reciprocity failure with strong frequency dependence occurs in the presence of thermal flux that is modulated by force: a non-equilibrium condition. Non-reciprocal effects give rise to a maximum enhancement of a factor of five in sensitivity.

A polyacrylamide gel route was introduced to synthesize LuFeO₃ particles, where the effects of calcination temperature, calcination time and chelating agent on the products were investigated. By varying the experimental conditions, several LuFeO₃ samples with sphere-, ellipsoid- and worm-like morphologies and average particle sizes of 200–270 nm were prepared. The photocatalytic activity of LuFeO₃ samples was evaluated by degrading rhodamine B (RhB) under simulated-sunlight irradiation, revealing that they exhibit a pronounced photocatalytic activity. The effects of p-benzoquinone (BQ), ethanol and oxalic acid (OA) on the photocatalytic efficiency were investigated. It is observed that BQ has almost no effect on the photocatalytic degradation of RhB, ethanol exhibits a substantial suppression of RhB degradation, while OA significantly enhances the photocatalytic efficiency. Hydroxyl (^•OH) radicals were examined by fluorimetry using terephthalic acid as a probe molecule, and are found to be produced over the simulated-sunlight irradiated LuFeO₃ particles. The addition of ethanol leads to a quenching of ^•OH radicals, whereas the yield of ^•OH radicals is highly increased on addition of OA. Based on the experimental results, ^•OH radicals are suggested to be the dominant active species responsible for the dye degradation, while superoxide (^•O₂⁻) radicals play a negligible role in the photocatalysis.

Gd³⁺ ion-substituted manganese ferrite nanoparticles with the chemical formula MnGd_xFe_2-xO₄ (x = 0.0, 0.05, and 0.1) were synthesized by sol–gel auto combustion method. Thermal stability of the as-prepared sample was analyzed using thermo gravimetric and differential thermal analysis (TG–DTA) and the result reveals that the prepared sample is thermally stable above 300 °C. Structural and morphology studies were performed using powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Indexed PXRD patterns confirm the formation of pure cubic spinel structure. The average crystallite sizes calculated using Sherrer's formula decreased from 47 nm to 32 nm and lattice constant was enhanced from 8.407 Å to 8.432 Å. The FTIR spectrum of manganese ferrite shows a high frequency vibrational band at 564 cm⁻¹ assigned to tetrahedral site and a low frequency vibrational band at 450 cm⁻¹ assigned to octahedral site which are shifted to 556 cm⁻¹ and 439 cm⁻¹ for Gd³⁺ substitution and confirm the incorporation of Gd³⁺ into manganese ferrite. SEM analysis shows the presence of agglomerated spherical shaped particles at the surface. Room temperature dielectric and magnetic properties were studied using broadband dielectric spectroscopy (BDS) and vibrating sample magnetometry (VSM). Frequency dependent dielectric constant, ac conductivity and tan delta were found to increase with Gd³⁺ ion substitution. The measured values of saturation magnetization decrease from 46.6 emu g⁻¹ to 41 emu g⁻¹ with increase in Gd³⁺ concentration and coercivity decreases from 179.5 Oe to 143 Oe.

We carry out an analysis of the paper published in Arda and Sever (2014 Phys. Scr.89 105204) and reveal several unclear points. In the first place, the derivation of the main equations does not appear to be correct. In the second place, the expression for the energy does not appear to yield the results reported by the authors. In the third place, they failed to indicate the references reporting the eigenvalues chosen for comparison. In the fourth place the eigenvalues reported by the authors do not show the same order as those of the Hellmann potential thus leading to a different underlying physics. What is more: the spectrum of the modified model is qualitatively different from the one supported by the Hellmann potential.

Contrary to what is conventionally assumed, to determine the location and flow of potential energy in vibrating strings, the effects of longitudinal displacements need to be taken into account, even when these displacements are much smaller than the associated transverse displacements. In a recent paper, Butikov (2013 Phys. Scr.88 065402) investigated the implications of this fact and found an infinitely long transverse travelling wave with associated longitudinal disturbance where the associated potential energy density apparently travelled along with the transverse wave at the transverse wave speed. This finding contradicts previous results with transverse pulses which show that in the presence of a unidirectional transverse travelling wave, potential energy propagates at the longitudinal not transverse wave speed. This apparent contradiction is reconciled in this paper by considering a finite length of Butikov's infinitely long travelling wave. It is shown that the energy flow found by Butikov is the net effect of potential energy propagating in both directions at the longitudinal wave speed, a fact that is hidden when a wave of infinite length is considered. This conclusion is supported by a general theoretical result. In addition, it is shown that Butikov's claim that the part of the potential energy density proportional to the first spatial derivative of the longitudinal displacement represents a relocation of the pre-existing potential energy which the string has due to the initial stretching required to create a tension in the string is only valid in a limited number of situations. In most of the examples considered, the term represents a relocation of the potential energy of the wave, though in general it can have many different physical interpretations.