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Congenital hypothyroidism is one of the most common preventable causes of mental retardation and clinical manifestations are often subtle or absent at birth and hence the need for screening. Implementation of newborn screening requires local normative values.To determine the normative values of cord Thyroid Stimulating Hormone (TSH) among term babies in Bauchi, Northeast Nigeria and compare it with that from other centers in Nigeria.Cord blood samples from 200 term babies were analyzed for TSH by Fluorescence Immunoassay technique in this descriptive cross-sectional study. A cut-off of20 µIU/ml was used for recall. The mean and range were determined and compared with those of previous local studies using t-test. Impact of some maternal and infant factors on TSH was also assessed.The overall mean (SD) cord TSH was 3.74 (±1.99) µIU/ ml and the range was 0.73 to 15.22 µIU/ml (2.5th to 97.5th centile) and none had TSH20 µIU/ml and hence our recall rate was 0%. The mean cord TSH was comparable to that reported by a lone local multicenter study (p = 0.120) but significantly different from that of 3 other local studies (p0.001). There was also no significant difference between the means of different gender, birth weight groups, mode of delivery, socio-economic classes, maternal age and parity.The Cord blood TSH level of most term newborn in Bauchi, similar to other Nigerian studies, is10 µIU/ml with a few but significant percentage recording cord TSH level10 µIU/ml. Gender, birth weight, mode of delivery, socio-economic class, maternal age and parity were not significantly related to cord TSH level. The mean blood TSH values from different studies across the country tend to vary based on the assay technique. We recommend a nationwide multicenter study with a much larger sample size, lower cutoff value for recall and a unified sample processing laboratory if national normative values are to be developed.L’hypothyroïdie congénitale est l’une des causes évitables les plus courantes de retard mental et les manifestations cliniques sont souvent subtiles ou absentes à la naissance, d’où la nécessité d’un dépistage. La mise en œuvre du dépistage néonatal nécessite des valeurs normatives locales. OBJECTIFS: Déterminer les valeurs normatives de l’hormone stimulatrice de la thyroïde (TSH) du cordon chez les bébés nés à terme à Bauchi, Nord-Est du Nigeria et les comparer à celles d’autres centres du Nigeria.Des échantillons de sang ombilical de 200 bébés nés à terme ont été analysés pour la TSH par la technique d’ étude descriptive transversale. Un seuil de20 µUI/ml a été utilisé pour le rappel. La moyenne et l’intervalle ont été déterminés et comparés avec ceux des études locales précédentes en utilisant le test t. L’impact de certains facteurs maternels myet infantiles sur la TSH a également été évalué.La moyenne globale (SD) de la TSH du cordon était de 3,74 (±1,99) µIU/ml et l’intervalle était de 0,73 à 15,22 µIU/ml (2,5 à 97,5 centiles) aucun n’avait une TSH20 µIU/ml et donc notre taux de rappel était de 0%. La moyenne de TSH au cordon était comparable à celle rapportée par une seule étude multicentrique locale unique (p = 0,120) mais significativement différente de celle de 3 autres études locales (p0,001). Il n’y avait pas non plus de différence significative entre les moyennes des différents sexes, groupes de poids de naissance, mode d’accouchement, classes socio d’accouchement, les classes socio-économiques, l’âge maternel et la parité.Le niveau de TSH dans le sang de cordon de la plupart des nouveau-nés à termede la plupart des nouveau-nés à terme à Bauchi, comme dans d’autres études nigérianes, est10 µUI/ml mais significatif, enregistrant un niveau de TSH du cordon10 µIU/ml. Le sexe, le poids à la naissance, le mode d’accouchement, la classe socio-économique maternelle et la parité n’étaient pas significativement liés au taux de TSH au cordon. Le site valeurs moyennes de la TSH sanguine provenant de différentes études dans le pays ont tendance à varier en fonction de la technique de dosage. Nous recommandons une étude nationale multicentrique avec une taille d’échantillon beaucoup plus grande, une valeur seuil pour le rappel et un laboratoire de traitement des échantillons unifié si des valeurs normatives nationales doivent être développées.Sang de cordon, Hormone de stimulation thyroïdienne, Bébés à terme.

The presence of heavy ions has a profound impact on the temporal response of the magnetosphere to internal and external forcing, and plays a key role in plasma entry and transport processes within the terrestrial magnetosphere.Numerous studies focused on the transport and energization of O+ through the ionosphere-magnetosphere system; however, relatively few have considered the contribution of N+ to the near-Earth plasma, even though past observations have established that N+ is a significant ion species in the ionosphere and its presence in the magnetosphere is significant. In spite of only 12% mass difference, N+ and O+ have different ionization potentials, scale heights and charge exchange cross sections. The latter, together with the geocoronal density distribution, plays a significant role in the formation of ENAs, which in turn controls the energy budget of the inner magnetosphere, and the overall loss of the ring current. Therefore, the outflow of N+ from the ionosphere, in addition to that of O+, affects the global structure and properties of the current sheet, the mass loading of the magnetosphere, and it leads to changes in the local properties of the plasma, which in turn can influence waves propagation. This study involves an integrated computational view of geospace, that solves and tracks the evolution of all relevant ion species, to systematically assess their regional and global influence on the various loss and acceleration mechanisms operating throughout the terrestrial magnetosphere. We employ the newly developed Seven Ion Polar Wind Outflow Model (7iPWOM), which in addition to tracking the transport of H+, He+ and O+, now solves for the heating and transport of N+, N2+, NO+ and O2+ in Earth’s polar wind. The 7iPWOM is coupled with a two-stream model of superthermal electrons (GLobal airglow, or GLOW) to account for the attenuated radiation, electron beam energy dissipation, and secondary electron impact. We show that during various solar conditions, the polar wind outflow solution using 7iPWOM improves significantly when compared with OGO observations. In addition, numerical simulations using the kinetic drift Hot Electron Ions Drift Integrator (HEIDI) model suggest that the contribution of outflowing N+ to the ring current dynamics is significant, as the presence of N+alters the development and the decay rate of the ring current. Electron transfer collisions are far more efficient at removing N+ the system, compared with the removal of O+ ions. Synthetic TWINS-like mass separated ENA images show that the presence on nitrogen ions in the ring current, even in small amounts, significantly alters the ENA fluxes, and the peak of oxygen ENA fluxes can vary for up to an order of magnitude, depending on the magnetosphere composition. These findings can explain recent observations of faster than expected decay of high energy oxygen ions, as measured by the RBSPICE instrument on board of the Van Allen Probe spacecraft. We speculate that the abundance of oxygen has been mis-estimated, as it is likely that some of the oxygen measurements to actually be include comparable abundances of nitrogen ions.

The problem of dispersion of geodesic acoustic modes is revisited with two different methods for the solution of the kinetic equation. The dispersive corrections to the mode frequency are calculated by including the m = 2 poloidal harmonics. Our obtained results agree with some earlier results but differ in various ways with other previous works. Limitations and advantages of different approaches are discussed.

The variation in surface morphology and plasma parameters of laser irradiated tungsten has been investigated as a function of irradiance. For this purpose, Nd:YAG laser (1064 nm, 10 ns, 10 Hz) is employed. Tungsten targets were exposed to various laser irradiances ranging from 6 to 50 GW/cm2 under ambient environment of argon at a pressure of 20 Torr. Scanning electron microscope analysis has been performed to analyze the surface modification of irradiated tungsten. It revealed the formation of micro- and nanoscale surface structures. In central ablated area, distinct grains and crack formation are observed, whereas peripheral ablated areas are dominated by cones and pinhole formation. It was observed that at irradiances exceeding a value of 13 GW/cm2, the morphological trend of the observed structures has been changed from erosion to melting and re-deposition dominant phase. Ablation efficiency as a function of laser irradiance has also been investigated by measuring the crater depth using surface profilometry analysis. It is found to be maximum at an irradiance of 13 GW/cm2 and decreases at high laser irradiances. In order to correlate the accumulated effects of plasma parameters with the surface modification, laser-induced breakdown spectroscopy analysis has been performed. The electron temperature and number density of tungsten plasma have been evaluated at various laser irradiances. Initially with the increase of the laser irradiance up to 13 GW/cm2, an increasing trend is observed for both plasma parameters due to enhanced energy deposition. Afterward, a decreasing trend is achieved which is attributed to the shielding effect. With further increase in irradiance, a saturation stage comes and insignificant changes are observed in plasma parameters. This saturation is explainable on the basis of the formation of a self-regulating regime near the target surface. Surface modifications of laser irradiated tungsten have been correlated with plasma parameters.

Spatial damping of electromagnetic (EM) waves propagating parallel to the ambient magnetic field in collisionless plasmas is discussed for thermal distribution of electrons. By using the exact numerical analysis, it is shown that the spatial damping properties in hot plasma can be significantly different than the customary cold plasma analysis. The discrepancy comes from the wave-particle interaction (cyclotron resonance) and higher order thermal effects. The response of plasma to the interacting EM radiation depicts the variety of changes in different frequency domains. The comparison with the analytical results based on the expansion of plasma dispersion function is also made in order to validate the approximate treatment and to under what regime full kinetic treatment is called for.

The Electrostatic Ion Cyclotron (EIC) instability that includes the effect of wave-particle interaction is studied owing to the free energy source through the flowing velocity of the inter-penetrating plasmas. It is shown that the origin of this current-less instability is different from the classical current driven EIC instability. The threshold conditions applicable to a wide range of plasma parameters and the estimate of the growth rate are determined as a function of the normalized flowing velocity ( u0/vtfe), the temperature ( Tf/Ts) and the density ratios ( nf0/ns0) of flowing component to static one. The EIC instability is driven by either flowing electrons or flowing ions, depending upon the different Doppler shifted frequency domains. It is found that the growth rate for electron-driven instability is higher than the ion-driven one. However, in both cases, the denser (hotter) is the flowing plasma, the lesser (greater) is the growth rate. The possible applications related to the terrestrial solar plasma environment are also discussed.

It is shown that the universally unstable kinetic drift wave in an electron-ion plasma can very effectively be suppressed by adding an extra flowing ion (or plasma) population. The effect of the flow of the added ions is essential, their response is of the type $({v}_{ph}\ensuremath{-}{v}_{f0})exp[\ensuremath{-}{({v}_{ph}\ensuremath{-}{v}_{f0})}^{2}]$, where ${v}_{f0}$ is the flow speed and ${v}_{ph}$ is the phase speed parallel to the magnetic field vector. The damping is strong and it is mainly due to this ion exponential term, and this remains so for ${v}_{f0}l{v}_{ph}$.

Anomalous skin effects (ASEs) are studied for the transverse electromagnetic waves in an unmagnetized collisionless plasma using anisotropic kappa distribution. The effects of the kappa spectral index (κ), temperature anisotropy ( A=T⊥/T||), and the wave frequency (ω) on the ASEs are highlighted to be applicable for a wide range of plasma parameters. It is shown that the skin depth is reduced in a kappa distributed plasma as compared to the Maxwellian one. The anisotropy may enhance/reduce the skin depth depending upon the wave frequency to plasma frequency ratio ( ω/ωp) and the regime of the anisotropy (i.e., A > 1 or A

Employing linearized Vlasov-Maxwell system, the Weibel instability embedded in an ambient magnetic field is discussed for a semi-relativistic bi-Maxwellian distribution hoping such a scenario occurs in some relativistic environments e.g., gamma-ray burst sources and relativistic jet sources, supernovae, and galactic cosmic rays where the perpendicular temperature is much dominated over the parallel . The dispersion relations are analyzed analytically along with the graphical representation and the estimates of the growth rate are presented along with the instability threshold condition in the limiting cases i.e., xi>1 (non-resonant case). It is observed that the relativistic effect suppresses the instability and also lowers the threshold for the instability to set in. The ambient magnetic field contribution to instability appears only in non-resonant case resulting in reduction of growth rate. However, the effect of the ambient magnetic field is diminished as we go from the weak relativistic regime to the highly relativistic one. We also note that the ambient magnetic field generates real oscillations and the reletivistic effect reduces these oscillations. Further for field free case i.e., B0=0, the growth rates for Weibel instabilities are also presented in a semi-relativistic bi- Maxwellian plasma for both the limiting cases., 15 pages

We present a fluid model for geodesic acoustic modes including diamagnetic effects due to inhomogeneous plasma density and temperature. Effects of ion parallel viscosity (pressure anisotropy), which allows to recover exactly the adiabatic index obtained in kinetic theory are considered. We show that diamagnetic effects lead to the positive up-shift of the GAM frequency and appearance of the second (lower frequency) branch related to the drift frequency. The latter is a result of modification of the degenerate (zero frequency) zonal flow branch which acquires a finite frequency or becomes unstable in regions of high temperature gradients.

The general dispersion relation of obliquely propagating magneto-sonic (MS) waves for the inhomogeneous and anisotropic plasmas is analyzed including the effect of wave-particle interaction. The numerical analysis is performed without expanding both the plasma dispersion and the modified Bessel functions to highlight the effects of density inhomogeneity and the temperature anisotropy. The obtained results are compared with the recent work [Naim et al., Phys. Plasmas 22, 062117 (2015)], where only drift mode near the magnetosonic frequency is investigated. In our paper, we additionally analyzed two related modes depicting that the drift effect leads to an asymmetric behavior in the dispersion properties of drift MS waves. The possible application to the solar coronal heating problem has also been discussed.

Using kinetic theory for homogeneous collisionless magnetized plasmas, we present an extended review of the plasma waves and instabilities and discuss the anisotropic response of generalized relativistic dielectric tensor and Onsager symmetry properties for arbitrary distribution functions. In general, we observe that for such plasmas only those electromagnetic modes whose magnetic field perturbations are perpendicular to the ambient magneticeld, i.e.,B1 \perp B0, are effected by the anisotropy. However, in oblique propagation all modes do show such anisotropic effects. Considering the non-relativistic bi-Maxwellian distribution and studying the relevant components of the general dielectric tensor under appropriate conditions, we derive the dispersion relations for various modes and instabilities. We show that only the electromagnetic R- and L- waves, those derived from them and the O-mode are affected by thermal anisotropies, since they satisfy the required condition B1\perpB0. By contrast, the perpendicularly propagating X-mode and the modes derived from it (the pure transverse X-mode and Bernstein mode) show no such effect. In general, we note that the thermal anisotropy modifies the parallel propagating modes via the parallel acoustic effect, while it modifies the perpendicular propagating modes via the Larmor-radius effect. In oblique propagation for kinetic Alfven waves, the thermal anisotropy affects the kinetic regime more than it affects the inertial regime. The generalized fast mode exhibits two distinct acoustic effects, one in the direction parallel to the ambient magnetic field and the other in the direction perpendicular to it. In the fast-mode instability, the magneto-sonic wave causes suppression of the firehose instability. We discuss all these propagation characteristics and present graphic illustrations.

The kinetic instability of the obliquely propagating drift magnetosonic wave for temperature anisotropic low beta plasmas is studied by using the gyro-kinetic model. The interplay between the temperature anisotropy and the density inhomogeneity free energy sources is discussed in order to provide stabilization of drift instability by the temperature anisotropy effect. It is shown that the anisotropy suppresses the growth rate when the anisotropy ratio Ae,i (=T⊥(e,i)/T∥(e,i)) is greater than unity, whereas it enhances the growth rate for Ae,i

Employing the reductive perturbation technique, Zakharov–Kuznetzov (ZK) equation is derived for dust acoustic (DA) solitary waves in a magnetized plasma which consists the effects of dust anisotropic pressure, arbitrary charged dust particles, Boltzmann distributed ions, and Kappa distributed superthermal electrons. The ZK solitary wave solution is obtained. Using the small-k expansion method, the stability analysis for DA solitary waves is also discussed. The effects of the dust pressure anisotropy and the electron superthermality on the basic characteristics of DA waves as well as on the three-dimensional instability criterion are highlighted. It is found that the DA solitary wave is rarefactive (compressive) for negative (positive) dust. In addition, the growth rate of instability increases rapidly as the superthermal spectral index of electrons increases with either positive or negative dust grains. A brief discussion for possible applications is included.

A generalized dispersion relation of obliquely propagating drift magnetosonic waves is derived by using the gyrokinetic theory for anisotropic low beta plasmas. The stability analysis applicable to a wide range of plasma parameters is performed to understand the stabilization mechanism of the drift magnetosonic instability and the estimation of the growth rate is also presented. It is noted that the growth rate of the drift instability enhances for small anisotropy (Ae,i = T⊥e,i/T∥e,i 1).

By using the full electromagnetic drift kinetic equations for electrons and ions, the general dispersion relation for geodesic acoustic modes (GAMs) is derived incorporating the electromagnetic effects. It is shown that m = 1 harmonic of the GAM mode has a finite electromagnetic component. The electromagnetic corrections appear for finite values of the radial wave numbers and modify the GAM frequency. The effects of plasma pressure βe, the safety factor q, and the temperature ratio τ on GAM dispersion are analyzed.

The purely growing ordinary (O) mode instability, first discussed by Davidson and Wu [Phys. Fluids 13, 1407 (1970)], has recently received renewed attention owing to its potential applicability to the solar wind plasma. In a series of papers, Ibscher, Schlickeiser, and their colleagues [Phys. Plasmas 19, 072116 (2012); ibid. 20, 012103 (2013); ibid. 20, 042121 (2013); ibid. 21, 022110 (2014)] revisited the O mode instability and extended it to the low-beta plasma regime by considering a counter-streaming bi-Maxwellian model. However, the O-mode instability is, thus, far discussed only on the basis of the marginal stability condition rather than actual numerical solutions of the dispersion relation. The present paper revisits the O-mode instability by considering the actual complex roots. The marginal stability condition as a function of the (electron) temperature anisotropy and beta naturally emerges in such a scheme.

The classic Bernstein mode instability driven by a perpendicular momentum ring distribution function is insensitive to the parallel distribution. However, in the relativistic treatment, owing to the inexorable coupling between the parallel and perpendicular momenta through the Lorentz factor, the parallel momentum distribution may affect the instability. This paper discusses such a problem by making use of a model parallel momentum distribution function. It is found that the parallel momentum spread only leads to the modification of the real frequency, but the instability growth rate is largely unaffected.

By using the gyrokinetic theory, the kinetic Alfven waves (KAWs) are discussed to emphasize the drift effects through the density inhomogeneity and the temperature anisotropy on their dispersion characteristics. The dependence of stabilization mechanism of the drift-Alfven wave instability on the temperature anisotropy is highlighted. The estimate of the growth rate and the threshold condition for a wide range of parameters are also discussed.

Using the Vlasov-Maxwell system of equations, the dispersion relations for the perpendicular propagating modes (i.e., X-mode, O-mode, and upper hybrid mode) are derived for a weakly magnetized relativistic degenerate electron plasma. By using the density (n0=pF3/3π2ℏ3) and the magnetic field values for different relativistic degenerate environments, the propagation characteristics (i.e., cutoff points, resonances, dispersions, and band widths in k-space) of these modes are examined. It is observed that the relativistic effects suppress the effect of ambient magnetic field and therefore the cutoff and resonance points shift towards the lower frequency regime resulting in enhancement of the propagation domain. The dispersion relations of these modes for the non-relativistic limit (pF2≪m02c2) and the ultra-relativistic limit (pF2≫m02c2) are also presented.

Using the quantum hydrodynamic model of plasmas, the stability analysis of self-gravitational electrostatic drift waves for a streaming non-uniform quantum dusty magnetoplasma is presented. For two different frequency domains, i.e., Ω0d≪ω

Using the Vlasov-Maxwell’s model, the generalized dispersion relations for parallel propagating electromagnetic modes (R- and L-waves) and electrostatic mode (Langmuir wave) for weakly magnetized relativistic degenerate plasma are derived. The propagation characteristics of these modes are analyzed both analytically and graphically in order to highlight the relativistic and the ambient magnetic field effects in different degenerate plasma environments. Furthermore, the analytical expressions of these modes are extracted for the limiting cases, i.e., non-relativistic (pF/moc≪1) and ultra-relativistic (pF/moc≫1). It is noted that the relativistic effects shift the cut-off point towards the lower value of frequency and resultantly broaden the propagation domain. Moreover, the cut-off point of R-wave/L-wave move towards the higher/lower frequency as the strength of ambient magnetic field is increased. The shifting of frequency due to the ambient magnetic field becomes more prominent in the non-relativistic re...

Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized electron plasma is presented and general expressions for longitudinal and transverse permittivites are derived. It is found that the penetration depth for R- and L-waves increases as we move from non-relativistic to highly relativistic regime. The ambient magnetic field reduces/enhances the skin effects for R-wave/L-wave as the strength of the field is increased. In general, the weak magnetic field effects are pronounced for the weakly relativistic regime as compared with other relativistic cases. The results are also graphically illustrated. On switching off the magnetic field, previous results for field free case are retrieved [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Priniples of Plasma Electrodynamics (Springer-Verlag, Berlin, Heidelberg, 1984), Vol. 9, p. 106].

Employing linearized Vlasov–Maxwell system, we derive a generalized dielectric tensor for a magnetized nonrelativistic bi-Maxwellian electron-ion plasma. Assuming low frequency waves in a low β plasma, a new dispersion relation describing oblique propagation of the Alfvenic modes is determined, incorporating the temperature anisotropies of both the electrons and ions and their finite Larmor radii effects. From the resulting dispersion relation for kinetic Alfven waves, analytical expressions are determined for both the kinetic (vt∥i⪡ω/k∥⪡vt∥e and me/mi⪡β⪡1) and the inertial (ω/k∥⪢vt∥e,i and β⪡me/mi) regimes. We observe that in both cases, the Alfvenic modes stand modified due to the acoustic effect arising from the temperature anisotropy, which may enhance or reduce the Alfven speed depending on the strength and signature of the anisotropies. A number of special cases are also retrieved under appropriate conditions.