Cross Field Research Articles

Asymptotic Behavior for the Vlasov--Poisson Equations with Strong External Magnetic Field. Straight Magnetic Field Lines

The subject matter of this paper concerns the Vlasov-Poisson equations in the framework of magnetic confinement. We study the behavior of the Vlasov-Poisson system with strong external magnetic field, when neglecting the curvature of the magnetic lines. The arguments rely on averaging techniques. We intend to determine second order approximations and to retrieve the usual electric cross field drift, the magnetic gradient drift, etc.

Fast sweeping probe system for characterization of spokes in E × B discharges.

We have developed a rapidly swept, back-to-back 100 kHz Langmuir probe system using a tunable compensating network to study the temporal evolution of low frequency oscillations in Penning discharges, Hall Thrusters, and other E × B discharges. Experimental validation of the probe system is performed at low and high sweeping frequencies in a stable Penning discharge. Then application of the probe system to measurements of plasma parameter fluctuations in a low frequency (4 kHz) rotating spoke and an analysis method using the Hilbert transform are shown. We find that the rotating spoke oscillation conducts approximately a third of the cross field current in our Penning device.

Management of patients with infectious diseases at Red Cross and Red Crescent field hospital in Bangladesh for refugees from Myanmar

Introduction: The Red Cross emergency hospital was opened in Cox’s Bazar, Bangladesh in October 2017. The hospital aims to provide vital health care including surgery to more than 500,000 of refugees fled from Myanmar in 2017. The 60-bed hospital is run by the Norwegian and Finnish Red Cross, and staffed by national medical personnel, including 15 doctors and 30 midwives from the Bangladesh Red Crescent Society, and a 30-strong team of international staff.

Experimental observation of drift wave turbulence in an inhomogeneous six-pole cusp magnetic field of MPD

This paper presents a detailed study on the controlled experimental observation of drift wave instabilities in an inhomogeneous six pole cusp magnetic field generated by an in-house developed multi-pole line cusp magnetic field device [Patel et al., Rev. Sci. Instrum. 89, 043510 (2018)]. The device is composed of six axially symmetric cusps and non-cusp (in between two consecutive magnets) regions. The observed instability has been investigated in one of these non-cusp regions by controlling the radial plasma density gradient with changing pole magnetic field which is a unique feature of this device. It has been observed that the frequency of the instability changes explicitly with the density gradient. Moreover, the scale lengths of plasma parameters, frequency spectrum, cross-correlation function, and fluctuation level of plasma densities have been measured in order to identify the instability. The cross field drift velocity due to fluctuation in plasma parameters has been measured from the wave number-frequency S (kz, ω) spectrum and verified with the theoretical values obtained from density scale length formula. Further, from the S (kz, ω) spectrum, it has been found that the drift velocity alternates the sign in the consecutive non-cusp regions.

Divertor leg filaments in NSTX-U

This paper presents the first observation of divertor localized turbulence in the NSTX-Upgrade spherical tokamak. Previous work in NSTX discharges (Maqueda et al 2010 Nucl. Fusion 50 075002) described fluctuations on the divertor target due to blobs generated on the low field side midplane. In the region that shows disconnection from upstream turbulence (private flux region and proximity of the strike point), divertor-localized fluctuations are observed via imaging of C III and D-α emission in diverted L-mode discharges and are characterized in this paper. Field-aligned filaments connected to the divertor target plate are radially localized at the separatrix on the outer divertor leg and in the private flux region on the inner divertor leg. These are limited to the region below the X-point with fluctuation levels up to 10%–20%. The filaments have comparable poloidal and radial correlation lengths (10–100 ion gyroradii ) and parallel correlation lengths of several meters. Toroidal mode numbers are in the range of 10–30 and 2–10 for outer and inner leg filaments. The poloidal motion of outer leg filaments has the same direction and comparable magnitude to advection due to drift calculated by the multi-fluid edge transport code UEDGE with inclusion of cross field drifts. Disconnection between inner and outer leg filaments as well as the absence of correlation with upstream turbulence support the hypothesis of X-point disconnection for divertor leg filaments. Simulations with the ArbiTER linear eigenvalue solver and a resistive-balooning model were performed with a simulation grid limited to the divertor legs. Instabilities localized to the bad curvature side of the divertor legs were observed, in qualitative agreement with the experiment.

The unseen power of creative news management in government

PurposeLabour came to power in 1997 and immediately transferred many features of its party political news management style into government, overseeing the departure of most of the civil service communications leadership within two years, and developing the media management role of politically appointed special advisers. The purpose of this paper is to empirically examine the changes in custom and practice that operated behind the scenes in government communications between 1997 and 2015, asking to what extent such changes challenge public trust in government in a liberal democracy.Design/methodology/approachThis study takes a longitudinal, qualitative approach through in-depth interviews with former civil servants, journalists and special advisers, together with documentary and archival evidence. The data were analysed thematically through the text-processing software, NVivo.FindingsThe paper finds that although the controversy over the 2002 dossier on Iraq’s Weapons of Mass Destruction was an extraordinary episode, the creative approach to news management that characterised this case still operates within UK Government communications: the bypassing of civil servants, a partial approach to the facts, selective briefing of favoured journalists, a lack of due process in the management of information and a disregard for the letter and spirit of propriety codes. This has implications for public trust and confidence in the workings of liberal democracy.Originality/valueThe study adopts a mediatisation approach to the study of public relations, using the concept of the “cross field” to demonstrate how PR professionals share media management responsibilities with a number of different promotional actors. PR professionals in government must therefore navigate between the hidden, competitive and demanding worlds of politics, the media and bureaucracy, working with journalists, politicians and political operatives to craft the narratives that seek to drive public opinion.

Role Differences in Healthcare: Overcoming Borders through Semiotic Skin is the Basis for Communication

Role differences in healthcare systems are the very foundation of communication in this specific field of environment. It has to be understood as a collective corporation between collective individuals and thus connect through intertwined border zones. These border zones between collective communicators holds the notions of individuality, which is represented in the ability to decipher and negotiate the multiple layers in the communicative border zone. These processes in border zones of persons - in relation with others - are dealt with by the Semiotic Skin Theory. In addition, the biological skin is central for human lives and the Semiotic Skin is conceptualized as a socio-somatic-semiotic, layered and dynamic membrane that operates as a semi-permeable, communicative boundary. A constant interpretation between a self-reflecting system and an unending spiral of semiosis is the emergent of the semiotic skin. It creates a semi-permeable barrier that holds the very notions of the multi-layered skin-on-the-skin that is reflected in an embodied communication between humans and environment. In this theoretical understanding of an embodied aspect of not only meaning-making but also the regulative aspect of embodied interaction with others, the very idea of borders of individuality becomes the notion of interpretation. Any communication in a medical setting involves actions on the border of mutual understanding - e.g. communication between a pediatrician and a child. The concepts of a collective patient and a collective doctor are introduced as to understand the aspects of the multiple dynamics of the semiotic skin as the holder of an individual's personal ideas/interpretations in the interaction with one other person, holding multiple aspects from others as well. Examples of the interaction between patients and the healthcare system in Denmark illustrate how a new theoretical and practical performance of mastering the communicative partnership in the cross field between the healthcare system and psychology is born.

Up/down impurity density asymmetries in C-Mod plasmas

Brightness profiles of x-ray emission from H-like Ar17+ exhibit a distinct up/down asymmetry under certain operating conditions in C-Mod plasmas, indicating that impurity densities are not constant on flux surfaces with r/a between ∼0.8 and ∼0.95. In L- and I-mode plasmas, there is an x-ray brightness excess, up to a factor of 8, on the side opposite to the ion B × B drift direction. This effect is not observed in H-mode plasmas, presumably due to edge impurity transport being dominated by a strong inward pinch, which is absent in L- and I-mode. The magnitude of the asymmetry in L- and I-mode decreases with increasing plasma current, similar to the observed decrease in radial impurity diffusivity. In I-mode, where the codependence between electron density and temperature can be broken with ICRF heating power, the asymmetry magnitude is found to decrease with increasing density and with increasing edge temperature at fixed density. These measurements exhibit some qualitative features of neo-classical expectations but the observed asymmetry magnitude is much larger than predicted and some scalings with plasma parameters are not seen. The up/down asymmetry appears to be largest when the cross field impurity diffusivity is the highest.

An invivo study of the pharmacological activities of a methanolic acetate fraction of Pistia stratiotes L.: An ethno-medicinal plant used in Bangladesh.

BackgroundThe present study covered an assessment of methanolic acetate fractions of Pistia stratiotes, commonly known as water lettuce, for analgesic, anti‐inflammatory, and CNS depressant activities.MethodsThe methanol acetate fractions were extracted from Pistia stratiotes and administered to the experimental animals as 200 and 400 mg/kg doses to determine the effect on acetic acid‐induced writhing and formalin‐induced licking and biting, for the assessment of analgesic activity. The anti‐inflammatory assay was done using the carrageenan‐induced hind paw edema method, while assessment of CNS depressant activity was done using the open field and hole cross tests. The effects were compared to standard reference drugs.ResultsAt both doses (200 and 400 mg/kg body weight), the methanolic acetate extract of P. stratiotes showed significant analgesic action (P < 0.05) against acetic acid‐induced writhing. The extract was also found to give significant protection against licking and biting at both doses. The methanolic acetate extract of P. stratiotes showed a significant (P < 0.05) anti‐inflammatory effect from 0 minutes up to 3 hours in the carrageenan‐induced paw edema test. In the CNS depressant assay, the methanolic acetate extract showed significant (P < 0.05) depressant activity at both doses from 30 to 120 minutes in both the hole cross and open field tests.ConclusionThus we can conclude that P. stratiotes extracts have significant analgesic, anti‐inflammatory, and CNS depressant activity, compared to standard compounds, in an animal model.

Neuropharmacological Activities of Methanol Extract of Albizia lebbeck (L.) Benth.

Albizia lebbeck (Linn.) Benth. is a deciduous tree which is planted as ornamental and avenue tree almost all over Bangladesh. Leaves of the plant are used in ethnomedicine for the treatment of convulsion and CNS related disorder. This study was aimed to evaluate the neuropharmacological effects of the methanol extract of A. lebbeck leaves in Swiss albino mice. The locomotor effect of crude methanol extract of the plant was investigated by open field and hole cross tests while the anxiolytic activity was determined using elevated plus-maze (EPM) and light/dark box (LDB) tests. Furthermore, the sedative activity of the plant extract was assessed by sodium thiopental-induced sleeping time test. The results demonstrated that the methanol extract significantly (p &lt; 0.001) reduced locomotion of the animals in both hole cross and open field tests in dose-dependent manner at 200-400 mg/kg b.w. In both EPM and LDB tests, the plant extract produced significant anxiolytic effect (p &lt; 0.05) at the doses of 100-400 mg/kg b.w. In addition, it showed significant (p &lt; 0.001) dose-dependent decrease in the onset of sleep and an increase in duration of sleep in sodium thiopental-induced sleeping time test. Preliminary phytochemical analyses of the plant extract revealed the presence of alkaloid, flavonoid, glycoside, saponin, tannin and resin. In acute toxicity test, the leaf extract did not exhibit any adverse effect in mice during 7 days treatment. The results of the present studies suggest that the crude methanol extract of A. lebbeck leaves possesses significant CNS depressant, anxiolytic and sedative properties and rationalize the traditional uses of the plant.Bangladesh Pharmaceutical Journal 21(2): 80-86, 2018

Integer-only cross field computation

We propose a new iterative algorithm for computing smooth cross fields on triangle meshes that is simple, easily parallelizable on the GPU, and finds solutions with lower energy and fewer cone singularities than state-of-the-art methods. Our approach is based on a formal equivalence, which we prove, between two formulations of the optimization problem. This equivalence allows us to eliminate the real variables and design an efficient grid search algorithm for the cone singularities. We leverage a recent graph-theoretical approximation of the resistance distance matrix of the triangle mesh to speed up the computation and enable a trade-off between the computation time and the smoothness of the output.

Plasmonic properties of spheroid silicon-silver nanoshells in prolate and oblate forms

Metal nanoparticles are excellent absorbers or scatterers of electromagnetic radiation, depending on their shape, size, material and refractive index of the surrounding medium. In studying the effect of shape, metallic core shell nanoparticle nanoparticles recently have attracted a great amount of interest in plasmonics due to the wide tunability of the plasmon resonances. In this paper, we have investigated the plasmonic properties of spheroid Silver-Silicon core shell nanoparticles, such as extinction, absorption and scattering cross sections and field enhancement factor as a function of parameters as: angle, wavelength and distance from the center. It has been shown that the localized surface plasmon resonance wavelength of these nanoparticles is severely dependent on shell thickness. The resonance wavelength of oblate core shell nanoparticle has a red shift relative to the prolate one. In both oblate and prolate core shell nanoparticles, field enhancement factor is extremely dependent on the shell thickness and in oblate core shell nanoparticle it’s dramatically greater than the prolate one in all distances from the center for all wavelengths and in both shapes, the maximum value of field enhancement factor take places in straight directions to applied field.

First three-dimensional edge plasma transport simulations with magnetic perturbations induced by lower hybrid waves on EAST

Recent experiments from the Experimental Advanced Superconducting Tokamak (EAST) show that lower hybrid waves (LHWs) can profoundly change the magnetic topology by inducing helical current filaments flowing along magnetic field lines in the scrape-off layer. Here, it is investigated for the first time how these magnetic perturbations caused by LHWs affect the edge plasma transport utilizing the three-dimensional Monte Carlo code EMC3-EIRENE, both in double-null and single-null configurations. The 3D magnetic topology structure is reflected in the plasma properties, due to much stronger parallel field transport compared with cross field diffusion. Good qualitative agreements between simulation results and experimental data from various edge diagnostics demonstrate that the EMC3-EIRENE code now is capable of taking into account the LHW-induced magnetic perturbation fields with both physical and geometrical effects being considered. Combined with experimental observations, the simulation results strongly support that total current amplitude of LHW-induced filaments increases with an increase in LHW input power. It can further deepen the penetration depth of the additional transport channel by extending the stochastic edge layer, and influence the ratio of heat (or particle) flux between split striated and original strike line on divertor targets. The 3D simulation results also indicate that the additional plasma transport channel induced by LHWs can significantly cause the redistribution of heat load between inner and outer divertor targets, which could not be found by the field line tracing method in previous works.

A non-invasive cancer gene detection technique using FLANN based adaptive filter

In recent years advancement in cross field technologies lead the world to the new era of genomic research. Several new technologies have been developed for early detection of critical genetic disease like cancer. Since the conventional morphological and clinical tests are invasive in nature and harmful to human body, researchers are intending to find a noninvasive way to predict cancer associated genes. They find accuracy as a major concern to be taken care of in disease gene identification system. Therefore the authors in this paper made an effort to raise the accuracy level compare to existing technique. Cancer is caused by changes in deoxyribonucleic acid sequence. If those changes can be identified, diseased gene can therefore be recognized exactly. Hence the authors compared the diseased gene with the healthy ones to capture the differences. In order to search such disparity more efficiently and accurately, functional link artificial neural network (FLANN) based adaptive filter with least mean squares algorithm is attempted in the present paper. FLANN filter offers trigonometric expansion of the input sequences which reduces the error to minimum value at faster rate. Here, cancer genes are distinguished from healthy genes based on amount of normalized mean square error, which is estimated through adaptive filter. 131 Genes are used to train the identifier and the proposed technique successfully identifies 369 test dataset. The database is collected from National Center for Biotechnology Information genbank. The performance of the overall system is investigated by measuring sensitivity, specificity and accuracy. The proposed algorithm achieves 86.85% accuracy compared to existing entropy based identifier. Overall system performance of the proposed FLANN based adaptive filter is displayed in receiver operating characteristic curve.

Experimental conditions to suppress edge localised modes by magnetic perturbations in the ASDEX Upgrade tokamak

Access conditions for full suppression of edge localised modes (ELMs) by magnetic perturbations (MP) in low density high confinement mode (H-mode) plasmas are studied in the ASDEX Upgrade tokamak. The main empirical requirements for full ELM suppression in our experiments are: 1. The poloidal spectrum of the MP must be aligned for best plasma response from weakly stable kink-modes, which amplify the perturbation, 2. The plasma edge density must be below a critical value, m−3. The edge collisionality is in the range (ions) and (electrons). However, our data does not show that the edge collisionality is the critical parameter that governs access to ELM suppression. 3. The pedestal pressure must be kept sufficiently low to avoid destabilisation of small ELMs. This requirement implies a systematic reduction of pedestal pressure of typically 30% compared to unmitigated ELMy H-mode in otherwise similar plasmas. 4. The edge safety factor q95 lies within a certain window. Within the range probed so far, , one such window, has been identified. Within the range of plasma rotation encountered so far, no apparent threshold of plasma rotation for ELM suppression is found. This includes cases with large cross field electron flow in the entire pedestal region.

Methanolic Extract of Peel of Citrus maxima Fruits Exhibit Analgesic, CNS Depressant and Anti-inflammatory Activities in Swiss Albino Mice

Objectives: This study investigates analgesic, CNS depressant and anti-inflammatory activities of crude methanolic extract of Peel of Citrus maxima fruits. Materials and Methods: Methanolic extracts of Citrus maxima peel with different concentration were tested for analgesic activity in mouse model of acetic acid induced writhing and formalin induced licking and biting. Anti-inflammatory effect was tested by carrageenan induced paw edema model and the CNS depressant activity was evaluated by observing the reduction of locomotors activity by hole cross and open field test. Results: The extract, at 500 mg/kg, showed higher analgesic activity (73.34%) against acetic acid induced pain in mice while the standard reference drug Diclofenac sodium exhibited 87.13% activity at 10 mg/kg dose. The test dose at 500 mg/kg produced 48.23% protection in formalin induced hind paw licking and biting compared to 54.11% protection by the reference drug (10 mg/kg Diclofenac sodium). The antiinflammatory effect of the extract was comparable to reference drug Ibuprofen and the effect was sustained for 2-4 hr. However, the extract also showed significant dose dependent CNS depressant activity. Conclusion: Methanolic extract of peel of Citrus maxima fruits has CNS depressant effect with moderate analgesic and anti-inflammatory properties.

Experimental Signatures of the Quantum Nature of Radiation Reaction in the Field of an Ultraintense Laser

The description of the dynamics of an electron in an external electromagnetic field of arbitrary intensity is one of the most fundamental outstanding problems in electrodynamics. Remarkably, to date there is no unanimously accepted theoretical solution for ultra-high intensities and little or no experimental data. The basic challenge is the inclusion of the self-interaction of the electron with the field emitted by the electron itself - the so-called radiation reaction force. We report here on the experimental evidence of strong radiation reaction, in an all-optical experiment, during the propagation of highly relativistic electrons (maximum energy exceeding 2 GeV) through the field of an ultra-intense laser (peak intensity of $4\times10^{20}$ W/cm$^2$). In their own rest frame, the highest energy electrons experience an electric field as high as one quarter of the critical field of quantum electrodynamics and are seen to lose up to 30% of their kinetic energy during the propagation through the laser field. The experimental data show signatures of quantum effects in the electron dynamics in the external laser field, potentially showing departures from the constant cross field approximation.

Fossil Conifer Woods from Cerro Piche Graben (Triassic–Jurassic?), North Patagonian Massif, Río Negro Province, Argentina

Fossil conifer woods are described for the first time in sedimentary rocks from Cerro Piche Graben, North Patagonian Massif, Argentina. The permineralized axes are chacaracterized by a pith constituted by parenchyma cells and a few sclerenchyma cells; secondary xylem homoxylic and pycnoxylic, without distinct growth rings; tracheid pits uniseriate and mainly spaced; cross fields cupressoid, with 3 to 8 pits; and rays homocellular, uniseriate and low. Based on these characteristics, the woods are assigned to Cupressinoxylon. Until now, the only fossil plants known from Cerro Piche were two specimens of Pleuromeia sp., which are reinterpreted also as conifer fossil remains.

Field‐Aligned Currents in Saturn's Nightside Magnetosphere: Subcorotation and Planetary Period Oscillation Components During Northern Spring

AbstractWe newly analyze Cassini magnetic field data from the 2012/2013 Saturn northern spring interval of highly inclined orbits and compare them with similar data from late southern summer in 2008, thus providing unique information on the seasonality of the currents that couple momentum between Saturn's ionosphere and magnetosphere. Inferred meridional ionospheric currents in both cases consist of a steady component related to plasma subcorotation, together with the rotating current systems of the northern and southern planetary period oscillations (PPOs). Subcorotation currents during the two intervals show opposite north‐south polar region asymmetries, with strong equatorward currents flowing in the summer hemispheres but only weak currents flowing to within a few degrees of the open‐closed boundary (OCB) in the winter hemispheres, inferred due to weak polar ionospheric conductivities. Currents peak at ~1 MA rad−1 in both hemispheres just equatorward of the open‐closed boundary, associated with total downward polar currents ~6 MA, then fall across the narrow auroral upward current region to small values at subauroral latitudes. PPO‐related currents have a similar form in both summer and winter with principal upward and downward field‐aligned currents peaking at ~1.25 MA rad−1 being essentially collocated with the auroral upward current and approximately equal in strength. Though northern and southern PPO currents were approximately equal during both intervals, the currents in both hemispheres were dual modulated by both systems during 2012/2013, with approximately half the main current closing in the opposite ionosphere and half cross field in the magnetosphere, while only the northern hemisphere currents were similarly dual modulated in 2008.

Noise Reduction in Cross field Devices

Noise Reduction in Cross field Devices