The shoreline hazard posed by ocean long waves such as tsunamis and meteotsunamis critically depends on the fraction of energy transmitted across the shallow near-shore shelf. In linear setting, bathymetric inhomogeneities of length comparable to the incident wavelength act as a protective high-pass filter, reflecting long waves and allowing only shorter waves to pass through. Here, we show that, for weakly nonlinear waves, the transmitted energy flux fraction can significantly depend on the amplitude of the incoming wave. The basis of this mechanism is the formation of dispersive shock waves (DSWs), a salient feature of nonlinear evolution of long water waves, often observed in tidal bores and tsunami/meteotsunami evolution. Within the framework of the Boussinesq equations, we show that the DSWs efficiently transfer wave energy into the high wavenumber band, where reflection is negligible. This is phenomenologically similar to self-induced transparency in nonlinear optics: small amplitude long waves are reflected by the bathymetric inhomogeneity, while larger amplitude waves that develop DSWs blueshift into the transparency regime and pass through. We investigate this mechanism in a simplified setting that retains only the key processes of DSW disintegration and reflection, while the effects such as bottom dissipation and breaking are ignored. The results suggests that the phenomenon is a robust, order-one effect. In contrast, the increased transmission due to the growth of bound harmonics associated with the steepening of the wave is weak. The results of the simplified modelling are validated by simulations with the FUNWAVE-TVD Boussinesq model.

The effects of axial magnetic field on the properties of the ions ejected from Nd:YAG laser (wavelength = 1064 nm, pulse duration = 6 ns) produced expanding Cu plasma were investigated. A plane Cu target, without and with 0.23 T axial magnetic field at its surface, was irradiated in the fluence range of 2–24 J/cm2. The ions emitted along the target surface normal were analyzed with the help of ion collector and time-of-flight electrostatic ion energy analyzer. The integrated ion yield, highest ion charge state, average ion energy, and energy of individual ion charge states were found to increase by application of the magnetic field. The initial parameters of the non-equilibrium plasma such as average ion charge, equivalent potential, electron temperature, electron density, Debye length, and transient electric field were estimated from the experimental results obtained without and with application of the magnetic field. The increase of ion yield and ion charge state by application of magnetic field are most probably due to the trapping of electrons in front of the target surface, which boosts up the electron impact ionization process. The ion energy increment due to the magnetic field is discussed in the frame work of electrostatic model for ion acceleration in laser plasma.

In this work, plasma is produced by irradiating a Ti target with 10 ns pulsed Nd:YAG (λ = 1064 nm) laser. The laser fluence at the target was varied in the range of 2–20.3 J/cm2. The ion signal from freely expanding Ti plasma in vacuum was characterized with the help of ion collector and time-of-flight electrostatic energy analyzer. The ion charge state was found to increase with the laser fluence and maximum available ion charge in this fluence range is Ti4+. A correlation between the intensities of various ion charge states was observed, which indicates that higher charge states are most probably produced through stepwise ionization mechanism. It is also observed that charge state distribution of plasma can be controlled by variation of the laser fluence. In addition, energy distribution of ion charge states Tin+ (n = 1–4) is measured by varying back plate voltage of the electrostatic energy analyzer for a fixed laser fluence of 20.3 J/cm2. Ions energy distributions were in the range of 0.36–3.0 keV and the most probable ion energy was found to increase linearly with ion charge state. The estimated equivalent potential at the laser fluence of 20.3 J/cm2 is about 310 V. These results are in good agreement with the predictions of electrostatic model of ion acceleration in laser plasma.

Fascioliasis is an important food-borne parasitic disease caused by the two trematode species, Fasciola hepatica and Fasciola gigantica. The phenotypic features of fasciolid adults and eggs infecting buffaloes inhabiting the Central Punjab area, Pakistan, have been studied to characterize fasciolid populations involved. Morphometric analyses were made with a computer image analysis system (CIAS) applied on the basis of standardized measurements. Since it is the first study of this kind undertaken in Pakistan, the results are compared to pure fasciolid populations: (a) F. hepatica from the European Mediterranean area; and (b) F. gigantica from Burkina Faso; i.e. geographical areas where both species do not co-exist. Only parasites obtained from bovines were used. The multivariate analysis showed that the characteristics, including egg morphometrics, of fasciolids from Central Punjab, Pakistan, are between F. hepatica and F. gigantica standard populations. Similarly, the morphometric measurements of fasciolid eggs from Central Punjab are also between F. hepatica and F. gigantica standard populations. These results demonstrate the existence of fasciolid intermediate forms in endemic areas in Pakistan.

Inductively coupled Ar-N2 plasma is characterized by Langmuir probe and optical emission spectroscopy (OES). The plasma parameters including electron temperature, electron number density and electron energy probability functions (EEPFs) are determined by the Langmuir probe for different discharge parameters such as rf power (10–100 W), filling pressure (0.02–0.4 mbar) and argon content (5–95%) in nitrogen discharge. Spectroscopic measurements enable the evaluation of active species concentration ([N],[N2]) in ground electronic state and dissociation fraction. Concentration of active species is increased with the increase in filling pressure in nitrogen discharge keeping argon as an actinometer. It is noticed that the actinometry is an efficient and reliable technique to calculate the concentration of ground electronic state of nitrogen species. Moreover, for different plasma conditions, the molecular dissociation fraction is enhanced, as the Ar content is increased from 5% to 95% in nitrogen discharge. It is found that that dissociation fraction strongly depends on filling pressure and Ar content in nitrogen discharge. Maximum dissociation is observed for 95% Ar at filling pressure of 0.06 mbar. It is also found that the plasma parameters and active species concentration significantly depend on discharge parameters and may be optimized by appropriate selection of discharge conditions.

Plasma was generated by focusing 10 ns Nd:YAG (λ = 1064 nm) laser pulse on the thick tungsten target. The laser fluence at the target was varied in the range of 3.57–10.97 J/cm2. The ion emission from the expanding tungsten plasma was analyzed with the help of an ion collector and time-of-flight electrostatic ion energy analyzer. About 44 times rise in the ion charge per laser shot was observed in the investigated laser fluence range. The measured threshold fluence for onset of the tungsten plasma was 3.27 J/cm2. The estimated plume expansion coefficient Zinf/Xinf = 2.5 ± 0.2 was in agreement with the previous experimental studies and the predictions of self-similar plume expansion model. The electrostatic ion energy analyzer study showed that charge state of the W ions increases with the laser fluence and maximum ion charge state was 5+. It was observed that threshold fluence for appearance of a specific charge state can be measured. A clear correlation between the relative abundances of W(n−1)+, Wn+, and W(n+1)+ indicates that higher order charge states are most probably produced by stepwise ionization process.

An experimental study on the pulsed laser ablation of copper by using Nd-YAG laser radiation of 1064 nm wavelength at a fluence of 13 J/cm2 is reported. A time-resolving plane Langmuir probe, placed at various angles with respect to the target surface normal, is used to record temporal variation of ion currents during the plasma expansion in vacuum. The measured angular distributions of integrated ion yields are strongly peaked in forward direction. The experimentally determined plume expansion coefficient Z inf/X inf = 2.1±0.2 is in good agreement with the previous studies. Time-of-flight measurements indicated that the energy of various ion components is highest along target surface normal and decreases with increase of the angle, however the effect of angle is more pronounced on the faster ions. The energy spread of the ions decreases approximately from ±670 eV to ±19 eV as the probe angle increases from 0° to 60°. The measured angular dependence of ion yield and most probable ion energy nicely follows the trends predicted by Anisimov's plume expansion model.

Plasma nitriding of aluminium in a 50 Hz pulsed-dc glow discharge is studied for different ion-current densities (2.0-5.0 mA cm-2) by keeping the corresponding discharge parameters such as treatment time, chamber pressure, substrate temperature and gas composition same. The treated samples are analysed for changes induced in surface properties using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Vickers's micro-hardness testing. XRD showed the downshift in the original diffraction peak corresponding to (111) plane reflection along with the emergence of new diffraction peak corresponding to (220) plane reflection, confirming the N-diffusion into existing Al-lattice and formation of AlN compound. Surface hardness is significantly improved which might be attributed to the diffusion of nitrogen and compound layer formation.

The ZnSx Se $_{1-x}$ (0 ≤x≤ 1) films were deposited on soda lime glass substrates by thermal evaporation technique. Optical and structural properties of these films were compared with the ZnSx Se $_{1-x}$ films deposited by various other techniques. XRD measurement showed that ZnSx Se $_{1-x}$ films are polycrystalline in nature with the preferred orientation along [111]. It was observed that the lattice constant decreases and the optical energy band gap increases with the sulfur content of the film. These results are in good agreement with the properties of ZnSx Se $_{1-x}$ films deposited by various other methods. Additionally, it was observed that the refractive index of a ZnSx Se $_{1-x}$ film decreases with increasing sulfur content. The results reported in this paper suggest that the lattice constants, optical energy band gap and refractive index of ZnSx Se $_{1-x}$ film can be tailored for a specific application by selecting suitable value of x.

Optical Emission Spectroscopy (OES) is used to investigate the effect of argon gas mixing on the electron temperature, the degree of nitrogen dissociation and the active species concentration in a 13.56 MHz radio frequency (RF) sustained nitrogen plasma. The electron temperature is determined from Ar-I emission line intensities by using the modified Boltzmann's plot method and is found to be increased with argon mixing in nitrogen plasma. The concentration of active species $\rm N_2(C ^3\Pi_{\it u})$ and $\rm N_2^+ (B ^2\Sigma_{\it u}^+)$ is monitored in terms of the emission intensities of nitrogen (0–0) bands of the second positive and the first negative systems respectively. The concentration of $\rm N_2 (C^3\Pi_{\it u})$ active species along with the degree of N2-dissociation is appreciably enhanced by argon mixing signifying the role of argon metastables in the excitation and dissociation processes.

Kinetic electron emission from MgO film under the impact of 50–300 eV rare-gas ions has been investigated by Monte Carlo simulation. The program includes excitation of the target electrons (by projectile ions, recoiling target atoms and fast primary electrons), subsequent transport and escape of these electrons from the target surface. Potential electron yields due to Auger neutralization of various ions are obtained by comparing the calculated kinetic electron yield with the experimental data. The program generates partial yields of the secondary electrons excited by projectile ions, recoiling target atoms and electron cascades. The partial yields of the electrons excited by projectile ions and electron cascades fluctuate with mass of the projectile ion like the electronic stopping. Moreover, lateral and depth distribution of the electrons excited by three excitation processes were quite different. For the range of investigated ion energies, the average electron escape depth was independent of the mass of the incident ion, which indicates that electron escape depth is a material property.