Cylindrical and spherical dust-ion-acoustic modified Gardner solitons in dusty plasmas with two-temperature superthermal electrons

A rigorous theoretical investigation has been performed on the propagation of cylindrical and spherical Gardner solitons (GSs) associated with dust-ion-acoustic (DIA) waves in a dusty plasma consisting of inertial ions, negatively charged immobile dust, and two populations of kappa distributed electrons having two distinct temperatures. The well-known reductive perturbation method has been used to derive the modified Gardner (mG) equation. The basic features (amplitude, width, polarity, etc.) of nonplanar DIA modified Gardner solitons (mGSs) have been thoroughly examined by the numerical analysis of the mG equation. It has been found that the characteristics of the nonplanar DIA mGSs significantly differ from those of planar ones. It has been also observed that kappa distributed electrons with two distinct temperatures significantly modify the basic properties of the DIA solitary waves and that the plasma system under consideration supports both compressive and rarefactive DIA mGSs. The present investigation should play an important role for understanding localized electrostatic disturbances in space and laboratory dusty plasmas where stationary negatively charged dust, inertial ions, and superthermal electrons with two distinct temperatures are omnipresent ingredients.     

Effect of dust size distribution on ion-acoustic solitons in dusty plasmas with different dust grains

Theoretical studies are carried out for ion acoustic solitons in multicomponent nonuniform plasma considering the dust size distribution. The Korteweg?de Vries equation for ion acoustic solitons is given by using the reductive perturbation technique. Two special dust size distributions are considered. The dependences of the width and amplitude of solitons on dust size parameters are shown. It is found that the properties of a solitary wave depend on the shape of the size distribution function of dust grains.     

Nonlinear dust-acoustic structures in space plasmas with superthermal electrons,positrons, and ions

Some features of nonlinear dust-acoustic (DA) structures are investigated in a space plasma consisting of superthermal electrons, positrons, and positive ions in the presence of negatively charged dust grains with finite-temperature by employing a pseudo-potential technique in a hydrodynamic model. For this purpose, it is assumed that the electrons, positrons, and ions obey a kappa-like (κ) distribution in the background of adiabatic dust population. In the linear analysis, it is found that the dispersion relation yield two positive DA branches, i.e., the slow and fast DA waves. The upper branch (fast DA waves) corresponds to the case in which both (negatively charged) dust particles and (positively charged) ion species oscillate in phase with electrons and positrons. On the other hand, the lower branch (slow DA waves) corresponds to the case in which only dust particles oscillate in phase with electrons and positrons, while ion species are in antiphase with them. On the other hand, the fully nonlinear analysis shows that the existence domain of solitons and their characteristics depend strongly on the dust charge, ion charge, dust temperature, and the spectral index κ. It is found that the minimum/maximum Mach number increases as the spectral index κ increases. Also, it is found that only solitons with negative polarity can propagate and that their amplitudes increase as the parameter κ increases. Furthermore, the domain of Mach number shifts to the lower values, when the value of the dust charge Z _d increases. Moreover, it is found that the Mach number increases with an increase in the dust temperature. Our analysis confirms that, in space plasmas with highly charged dusts, the presence of superthermal particles (electrons, positrons, and ions) may facilitate the formation of DA solitary waves. Particularly, in two cases of hydrogen ions H⁺ (Z _i = 1) and doubly ionized Helium atoms He²⁺ (Z _i = 2), the mentioned results are the same. Additionally, the mentioned dusty plasma does not support DA solitons with positive polarity (compressive solitons). Furthermore, our analysis confirms that DA double layers cannot exist in such a system. Moreover, the positron density has not a considerable effect on the behavior of DA solitons in our model.     

Excitation of dissipative drift turbulence in dusty plasmas

Drift instability in dusty plasma due to plasma density inhomogeneity and inhomogeneities of dust distributions in densities and charges is studied analytically. An explicit general expression for the growth rate of instability is derived. It is found that the growth rate of the dissipative drift instability is substantially enhanced and the threshold of the instability is lowered in the presence of dust.     

Ordered dusty structures in nuclear-track neon and argon plasmas

Ordered dusty structures formed of spherical monodisperse and polydisperse grains are obtained for the first time in a nuclear-track plasma produced by α-particles and fission fragments of ²⁵²Cf nuclei passing through neon or argon. A theoretical model of such a plasma is proposed. Monte Carlo computer simulations based on this model are carried out to explain the formation of such structures.     

Solitary waves in dusty plasmas with weak relativistic effects in electrons and ions

Two distinct classes of dust ion acoustic (DIA) solitary waves based on relativistic ions and electrons, dust charge Z _d and ion-to-dust mass ratio Q’ = m _i /m _d are established in this model of multicomponent plasmas. At the increase of mass ratio Q’ due to increase of relativistic ion mass and accumulation of more negative dust charges into the plasma causing decrease of dust mass, relativistic DIA solitons of negative potentials are abundantly observed. Of course, relativistic compressive DIA solitons are also found to exist simultaneously. Further, the decrease of temperature inherent in the speed of light c causes the nonlinear term to be more active that increases the amplitude of the rarefactive solitons and dampens the growth of compressive solitons for relatively low and high mass ratio Q’, respectively. The impact of higher initial streaming of the massive ions is observed to identify the point of maximum dust density N _d to yield rarefactive relativistic solitons of maximum amplitude.     

Small-amplitude shock waves and double layers in dusty plasmas with opposite polarity charged dust grains

Theoretical investigation is carried out for understanding the properties of nonlinear dust-acoustic (DA) waves in an unmagnetized dusty plasma whose constituents are massive, micron-sized, positive and negatively charged inertial dust grains along with q (nonextensive) distributed electrons and ions. The reductive perturbation method is employed in order to derive two types of nonlinear dynamical equations, namely, Burgers equation and modified Gardner equation (Gardner equation with dissipative term). They are also numerically analyzed to investigate the basic features (viz., polarity, amplitude, width, etc.) of shock waves and double layers. It has been observed that the effects of nonextensivity, opposite polarity charged dust grains, and different dusty plasma parameters have significantly modified the fundamental properties of shock waves and double layers. The results of this investigation may be used for researches of the nonlinear wave propagation in laboratory and space plasmas.     

Numerical simulations of ion and electron transport in a low-temperature dusty plasma

Charged particle transport and kinetic processes in a low-temperature dusty plasma are numerically simulated. Dust grains are represented as spheres with a given radius. The self-consistent electric field in the plasma surrounding a charged dust grain is calculated taking into account the perturbations of plasma quasineutrality near the grains. It is shown that applying an external electric field leads to a rearrangement of the plasma space charge and a break of the spherical symmetry of the electron and ion density distributions around the grain. The mutual influence of two identical charged dust grains is considered, and the energy of the electrostatic interaction between the grains is calculated. It is shown that this energy has a minimum at a certain finite distance between the grains.     

Drift and geodesic effects on the ion sound eigenmode in tokamak plasmas

A kinetic treatment of geodesic acoustic modes (GAMs), taking into account ion parallel dynamics, drift and the second poloidal harmonic effects is presented. It is shown that first and second harmonics of the ion sound modes, which have respectively positive and negative radial dispersion, can be coupled due to the geodesic and drift effects. This coupling results in the drift geodesic ion sound eigenmode with a frequency below the standard GAM continuum frequency. Such eigenmode may be able to explain the split modes observed in some experiments.     

Effects of supraoptimal temperatures on the myxomycetePhysarum polycephalum

Vibrio parahaemolyticus, the flagellated nonswarming marine bacteria were induced to swarm on solid media under three different conditions: growth at 20–26°C on medium containing 1% NaCl, growth on a medium in a sealed Petridish and growth on H₂O₂-treated medium. The morphological transformations observed in cells during swarming of V. parahaemolyticus are similar to those found jor the naturally swarming Vibrio alginolyticus. The mechanism of swarming in both species involves massive formation of peritrichous flagella and a negative chemotactive response to metabolic byproducts.     

Fast ion loss-driven H-mode transition in RF discharge plasmas of the Uragan-3M torsatron

In the l = 3 Uragan-3M (U-3M) torsatron with a helical divertor the plasma is produced and heated by RF field in the ω ≤ ω _ci range of frequencies. A two-temperature ion perpendicular energy distribution with a suprathermal tail sets in with heating. If the heating power is high enough, a spontaneous transition to an H-like confinement mode is observed. Recently, it has been supposed that the transition is connected with hotter and suprathermal ions (common name “fast ions“, FI) loss. The objective of this work is an experimental elucidation of the real link between the H-transition and FI loss. To do this, a transient regime of the RF discharge with two H-mode states is chosen, and the evolution is followed of electron density, FI content in the confinement volume, FI outflow to the divertor and edge potential. On the basis of juxtaposing of these processes, a conclusion is made that the H-mode transition in U-3M is really driven by FI loss. Possible mechanisms resulting in the transition are discussed, among them the ion orbit loss and the radial drift of helically-trapped ion orbits seem most probable.     

Spectroscopic measurements of the electron and ion temperatures and effective ion charge in current sheets formed in two- and three-dimensional magnetic configurations

The spatial distributions of the electron temperature and density, the effective and average ion charges, and the thermal and directed ion velocities in current sheets formed in two-dimensional magnetic fields and three-dimensional magnetic configurations with an X line were studied using spectroscopic and interference holographic methods. The main attention was paid to studying the time evolution of the intensities of spectral lines of the working-gas (argon) and impurity ions under different conditions. Using these data, the electron temperature was calculated with the help of an original mathematical code based on a collisional-radiative plasma model incorporating the processes of ionization and excitation, as well as MHD plasma flows generated in the stage of the current-sheet formation. It is shown that the electron temperature depends on the longitudinal magnetic field, whereas the ion temperature is independent of it. The effective ion charge of the current-sheet plasma was determined for the first time.     

Effects of low temperatures on in vitro produced bovine zygotes

The objective of this research was to investigate the effects of cooling on the development of bovine zygotes. One-cell bovine embryos were maintained at 39°C (control), 20°C, 10°C, or 0°C for 5, 10, or 20 minutes, then cultured in vitro for 7 days and the proportion of embryos developing to the compact morula or blastocyst stage compared between different treatments. Duration of exposure time had no effect on development. Development rates to the compact morula or blastocyst stage were 3.9%, 11.4%, 17.4%, and 24.4% for zygotes maintained at 0°C, 10°C, 20°C, and 39°C, respectively, with differences in embryo yield between every treatment (P < 0.05). In a second experiment, bovine pronuclei (karyoplasts) and cytoplasts were cooled at 0°C or maintained at 39°C for 5 minutes. Pronuclear transplantation was then utilized to create 4 types of reconstructed embryos, those with: 1) non-cooled pronuclei and non-cooled cytoplasm, 2) non-cooled pronuclei and cooled cytoplasm, 3) cooled pronuclei and non-cooled cytoplasm, and 4) cooled pronuclei and cooled cytoplasm. The proportion of embryos developing to the blastocyst stage was highest when non-cooled pronuclei were transferred into non-cooled cytoplasm (18.9%), and similar to that of non-cooled, non-manipulated control zygotes (13.2%, P > 0.05). No embryos developed to the blastocyst stage when pronuclei (cooled or non-cooled) were transferred into cooled cytoplasm. However, zygotes with cooled pronuclei transferred into non-cooled cytoplasm yielded 4.5% blastocysts (P < 0.05). More embryos developed to the compact morula or blastocyst stage when non-cooled vs. cooled cytoplasm was utilized, regardless of whether the pronuclei were cooled (P < 0.05). These data demonstrate that pronuclei are more tolerant to low temperature exposure than is ovum cytoplasm. Mol. Reprod. Dev. 47:435–439, 1997. © 1997 Wiley-Liss, Inc.     

Effects of body and head positions on bilateral difference in tympanic temperatures

We have examined the nonparallel changes in tampanic membrane temperatures (T _ty) from the two ears in response to various changes in body and head positions. Upon assuming a lateral recumbent position, the T _ty on the lower side increased while that on the upper side decreased. Pressure application over a wide area of the lateral chest only caused inconsistent and obscure asymmetric changes in T _ty. A lateral flexion of the head with the subject sitting upright and a rotation of the head to the side in a supine position induced an increase in the T _ty on the lower side compared to that on the upper side. The temperature and blood flow of the forehead often decreased on the lower side and increased on the upper side, although such responses were not always concomitant with the asymmetric changes in T _ty. A dorsal flexion of the head with the subject in a reclining position caused a slight increase in the T _ty, whereas raising the head upright induced a slight decrease in them. Two additional experiments were carried out with single photon emission computed tomography using ^99mTc-hexamethylpropyleneamine oxime as tracer, and a slight, relative decrease in counts was noted in the right hemisphere during rotation of the head to the right. These results would strongly suggest that unilateral increases and decreases in T _ty could have been caused by one-sided decreases and increases, respectively, in blood flow to the brain and/or the tympanic membrane, induced by a vasomotor reflex involving vestibular stimulation.     

Effects of rectal and ambient temperatures and humidity on conception rates

One hundred and thirteen inseminations were performed for which rectal temperatures were taken at the time of inseminations. Climatological factors were also recorded daily. Pregnancy diagnosis by rectal palpation was carried out 3 months post-insemination. Pregnancy rates for all services were related to selected climatological measurements and rectal temperatures. The results obtained indicate that elevated rectal temperature, mean maximum and mean minimum temperatures and relative humidity were detrimental to conception. The effect of the climatological factor on conception is compounded by feed scarcity during the dry periods of the year.     

Effects of salinity and phosphate on ion distribution in lupin leaflets

Lupin ( Lupinus luteus L. cv. Weiko III) were grown in nutrient solution over a range of inorganic phosphate (P_i) concentrations, with or without 50 m M NaCl. Plants with high P_i (2 m M ) and salt showed progressive leaf necrosis and had higher concentrations of total phosphate than plants grown with high P_i alone. Most of the extra total phosphate in salt treated plants was in the P_i form. P_i supply did not influence Na⁺, K⁺ or Cl⁻ concentrations in epidermal vacuoles or mesophyll cells. However, epidermal vacuoles accumulated more monovalent cations (Na⁺ and K⁺) than Cl⁻, and in vacuoles of plants grown with 0.1 m M P_i additional P_i was accumulated, possibly to maintain charge balance. Plants grown with 2 m M P_i did not accumulate additional P_i in epidermal vacuoles, but showed higher phosphorus levels in cell walls. It is suggested that at moderate phosphorus concentrations P_i plays a role in epidermal osmotic adjustment, possibly explaining the beneficial role of additional phosphorus on salt stressed plants. At high P_i supply with salt, P_i does not contribute to osmotic adjustment and instead accumulates in cell walls. However, the cause of leaf damage under conditions of high phosphorus supply and salinity is still not entirely clear.     

Effects of potassium ion supplementation on survival and ion regulation in Gulf killifish Fundulus grandis larvae reared in ion deficient saline waters

Teleost fish often live in an environment in which osmoregulatory mechanisms are critical for survival and largely unknown in larval fish. The effects of a single important marine ion (K⁺) on survival and ion regulation of larval Gulf killifish, an estuarine, euryhaline teleost, were determined. A four-week study was completed in four separate recirculating systems with newly hatched larvae. Salinity in all four systems was maintained between 9.5 and 10‰. Two systems were maintained using crystal salt (99.6% NaCl) with K⁺ supplementation (1.31 ± 0.04 mmol/L and 2.06 ± 0.04 mmol/L K⁺; mean ± SEM), one was maintained with crystal salt and no K⁺ supplementation (0.33 ± 0.05 mmol/L K⁺), the fourth system was maintained using a standard marine mix salt (2.96 ± 0.04 mmol/L K⁺), the salt mix also included standard ranges of other ions such as calcium and magnesium. Larvae were sampled throughout the experiment for dry mass, Na⁺/K⁺-ATPase (NKA) activity, whole body ion composition, relative gene expression (NKA, Na⁺/K⁺/2Cl^? cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR)), and immunocytochemistry staining for NKA, NKCC, and CFTR. Larvae stocked into water with no K⁺ supplementation resulted in 100% mortality within 24 h. Mortality and dry mass were significantly influenced by K⁺ concentration (P ≤ 0.05). No differences were observed among treatment groups for NKA activity. At 1 dph NKA mRNA expression was higher in the 0.3 mmol [K⁺] group than in other treatment groups and at 7 dph differences in intestinal NKA and CFTR staining were observed. These data indicate that the rearing of larval Gulf killifish may be possible in ion deficient water utilizing specific ion supplementation.     

Transition temperatures of the electrical activity of ion channels in the nerve membrane

The temperature dependence of some of the electrical characteristics of neuronal membranes from Aplysia giant neurons and crustacean and cuttlefish giant axons has been analyzed. Arrhenius plots for the maximum rate of depolarization of (V+max) or repolarization (V-max) of the action potential, for the resting membrane conductance, and for the speed of propagation of the action potential, exhibited clear breaks at characteristic temperatures between 17 and 20 degrees C. Lobster giant axons and frog nodes of Ranvier were voltage-clamped at different temperatures between 5 and 30 degrees C. Arrhenius plots for relaxation times related to the opening and closing processes affecting the Na+ and K+ channels were linear. No 'transition' temperature was detected. However, clear-cut changes in (Formula: see text) Na+ and K+ currents, were consistantly observed around 18 degrees C. Values for (Formula: see text) plateaued above 18 degrees C, then decreased gradually as a function of reduced temperature. Variations in temperature between 1 and 30 degrees C did not alter the binding properties of [3H]tetrodotoxin to a purified crab axonal membrane. Pharmacological properties of the Na+ channel are sensitive to temperature. The temperature-dependent effect of veratridine has been studied and indicates a change in properties of the Na+ channel below 20 degrees C. These results support the possibility that the fluidity of membrane lipids in the ionic channel microenvironment may influence the degree to which the channel can open.