Neutral Fluid Research Articles

Effects of positive dust component on self-gravitational instabilities of electromagnetic waves in dusty plasmas

An investigation has been carried out on the electromagnetic modes and associated instabilities in a partially ionized, nonuniform, self-gravitating positively and negatively charged dusty plasma, showing the effects of the inhomogeneities in the external magnetic field and the plasma number density, the neutral fluid dynamics, the drag forces, etc. The effects of these factors have been treated both analytically and numerically. The factors that stabilize the low frequency electromagnetic waves in the dusty plasma under consideration could be responsible to form the astrophysical objects in the galaxies.

Forced fluid removal versus usual care in intensive care patients with high-risk acute kidney injury and severe fluid overload (FFAKI): study protocol for a randomised controlled pilot trial

BackgroundIntravenous administration of fluids is an essential part of critical care. While some fluid administration is likely beneficial, there is increasing observational evidence that the development of fluid overload is associated with increased mortality. There are no randomised trials to confirm this association in patients with acute kidney injury. We aim to perform a pilot trial to test the feasibility of forced fluid removal compared to standard care in patients with acute kidney injury and severe fluid overload, the FFAKI trial.MethodsThen FFAKI trial is a pilot, multicentre, randomised clinical trial recruiting adult intensive care patients with acute kidney injury and fluid overload, defined as more than 10% of ideal bodyweight. Patients are randomised with concealed allocation to either standard care or forced fluid removal with a therapeutic target of negative net fluid balance ≥1 mL/kg/h. The safety of fluid removal is continually evaluated according to predefined criteria of hypoperfusion: lactate ≥4 mmol/L, mean arterial pressure <50 mmHg or mottling beyond the edge of the kneecaps. If patients fulfil one of these criteria, fluid removal is suspended until hypoperfusion has resolved. The primary outcome measure is fluid balance at 5 days after randomisation and secondary outcomes include mean daily fluid balance, fluid balance at discharge from the intensive care unit, time to neutral fluid balance, number of serious adverse reactions and number of protocol violations. All patients are followed for 90 days.DiscussionThe FFAKI trial started in October 2015 and, when completed, will provide data to evaluate whether a large trial of forced fluid removal in critically ill patients is feasible. Our primary outcome will show if the experimental intervention leads to a clinically relevant difference in fluid balance, which could prove beneficial in intensive care patients with acute kidney injury.Trial registrationEudraCT, identifier: 2015-001701-13. Registered on 19 September 2015;ClinicalTrials.gov, identifier: NCT02458157. Registered on 21 May 2015;Danish Ethics Committee, identifier: H-15009589H. Registered on 22 September 2015; Danish Health and Medicines Authority, identifier: 2015070013. Registered on 11 August 2015.

The Use of Stroke Volume Variation to Guide Donor Management Is Associated With Increased Organs Transplanted per Donor.

There is a national shortage of organs available for transplantation, and utilization rates for thoracic organs are less than 40%. In addition, the optimal method of assessing cardiovascular status during donor management is uncertain. FloTrac is a noninvasive hemodynamic technique that measures cardiac output and fluid responsiveness. Our objective was to measure the impact of using this technique to guide management on fluid balance, vasopressor usage, thyroid hormone usage, and pulmonary function. We hypothesized that FloTrac guidance will increase thoracic organs transplanted per donor (OTPD). Data were prospectively collected on a convenience sample of 38 donors after neurologic determination of death. Organs transplanted, net fluid balance, dosage of vasopressors, dosage of thyroid hormone, and Pao2:Fio2 were compared between treatment and control groups. The treatment group had greater thoracic OTPD (1.3 [1.0] vs 0.4 [0.6], P = .004) and overall OTPD (4.3 [1.5] vs 2.7 [1.5], P = .002). Donors in the treatment group maintained a neutral fluid balance, had more thyroid hormone used, and had an improvement in oxygenation. The implementation of this technology to aid providers may help ameliorate the shortage of thoracic and overall organs available for transplantation.

Plasma turbulence at ion scales: a comparison between particle in cell and Eulerian hybrid-kinetic approaches

Kinetic-range turbulence in magnetized plasmas and, in particular, in the context of solar wind turbulence has been extensively investigated over the past decades via numerical simulations. Among others, one of the widely adopted reduced plasma models is the so-called hybrid-kinetic model, where the ions are fully kinetic and the electrons are treated as a neutralizing (inertial or massless) fluid. Within the same model, different numerical methods and/or approaches to turbulence development have been employed. In the present work, we present a comparison between two-dimensional hybrid-kinetic simulations of plasma turbulence obtained with two complementary approaches spanning approximately two decades in wavenumber – from the magnetohydrodynamics inertial range to scales well below the ion gyroradius – with a state-of-the-art accuracy. One approach employs hybrid particle-in-cell simulations of freely decaying Alfvénic turbulence, whereas the other consists of Eulerian hybrid Vlasov–Maxwell simulations of turbulence continuously driven with partially compressible large-scale fluctuations. Despite the completely different initialization and injection/drive at large scales, the same properties of turbulent fluctuations at $k_{\bot }\unicode[STIX]{x1D70C}_{i}\gtrsim 1$ are observed, where $k_{\bot }$ is the fluctuations’ wavenumber perpendicular to the background magnetic field and $\unicode[STIX]{x1D70C}_{i}$ is the ion Larmor radius. The system indeed self-consistently ‘reprocesses’ the turbulent fluctuations while they are cascading towards smaller and smaller scales, in a way which actually depends on the plasma beta parameter ($\unicode[STIX]{x1D6FD}$ is the ratio between the thermal and the magnetic pressures). Small-scale turbulence has been found to be mainly populated by kinetic Alfvén wave (KAW) fluctuations for $\unicode[STIX]{x1D6FD}\geqslant 1$, whereas KAW fluctuations are only sub-dominant for low-$\unicode[STIX]{x1D6FD}$.

LA-ICP-MS trace element geochemistry of garnets: Constraints on hydrothermal fluid evolution and genesis of the Xinqiao Cu–S–Fe–Au deposit, eastern China

The Xinqiao Cu–S–Fe–Au deposit in the Tongling ore district, an important part of the Middle-Lower Yangtze River Valley metallogenic belt in eastern China, is located along the northern margin of the Yangtze Block. The deposit consists of two major mineralization types: stratiform and skarn (the genesis of the former is disputed). The more important stratiform orebody (90% of the total Cu, S and Fe reserves) has abundant garnet as the main gangue mineral, similar to the skarn orebody hosted in the intrusive contact.Garnets from the Xinqiao stratiform orebody range from pure andradite (And100) to And50Gro46, and can be divided into the early (Grt1) and late (Grt2) generation. Both generations contain low MnO (0.19–0.89%), wide range of Y/Ho (39.0–40.7 for Grt1, 29.8–67.9 for Grt2), and do not contain melt or fluid-melt inclusions, indicative of a magmatic-hydrothermal replacement origin. Grt1 and the Grt2 cores are grandite, whilst the Grt2 rims are mainly andradite with some grandite zones. Grandite is enriched in heavy rare earth elements (HREEs), and displays low ΣLREE/ΣHREE, LaN/YbN and U concentrations with negative Eu anomalies, whereas andradite is HREE-depleted, and displays high ΣLREE/ΣHREE, LaN/YbN ratios and U concentrations with positive Eu anomalies. The distinct trace element features suggest that the hydrothermal fluids for Grt1 and the Grt2 cores were of nearly neutral (pH), relatively oxidized and HREE-enriched, whereas those for the Grt2 rims had experienced episodic inflections between a mildly acidic, relatively reduced and HREE-depleted fluid and a nearly neutral, relatively oxidized and HREE-enriched fluid. Meanwhile, they also reveal that Grt1 and the Grt2 cores may have formed by diffusive metasomatism in a closed system, whereas the Grt2 rims may have formed by infiltration metasomatism in an open fracture system, possibly related to the unconformity that hosts the Xinqiao stratiform orebody. We propose that the Xinqiao stratiform orebody may have formed from Early Cretaceous magmatic-hydrothermal fluids associated with the Jitou stock, similar to the skarn-type orebodies in the district.

Gravitational shock wave inside a steadily accreting spherical charged black hole

We numerically investigate the interior of a four-dimensional, spherically symmetric charged black hole accreting neutral null fluid. Previous study by Marolf and Ori suggested that late infalling observers encounter an effective shock wave as they approach the outgoing portion of the inner horizon. Non-linear perturbations could generate an effective gravitational shock wave, which manifests as a drop of the area coordinate $r$ from inner horizon value $r_{-}$ towards zero in an extremely short proper time duration of the infalling observer. We consider three different scenarios: a) A charged black hole accreting a single (ingoing) null fluid; b) a charged black hole perturbed by two null fluids, ingoing and outgoing; c) a charged black hole perturbed by an ingoing null fluid and a self-gravitating scalar field. While we do not observe any evidence for a gravitational shock in the first case, we detect the shock in the other two, using ingoing timelike and null geodesics. The shock width $\Delta\tau$ decreases rapidly with a fairly good match to a new, generalized exponential law, $\Delta\tau\sim e^{-\intop\kappa_{-} (\widetilde{V}_{f})d\widetilde{V}_{f}}$, where $\widetilde{V}_{f}$ is a specific timing parameter for the ingoing timelike geodesics and $\kappa_{-}(\widetilde{V}_{f})$ is a generalized (Reissner-Nordstr\"om like) surface gravity of the charged black hole at the inner horizon. We also gain new insight into the inner (classical) structure of a charged black hole perturbed by two null fluids, including strong evidence for the existence of a spacelike $r=0$ singularity. We use a finite-difference numerical code with double-null coordinates combined with an adaptive gauge method in order to solve the field equations from the region outside the black hole down to the vicinity of the $r=0$ singularity.

Hall Effect–Mediated Magnetic Flux Transport in Protoplanetary Disks

Abstract The global evolution of protoplanetary disks (PPDs) has recently been shown to be largely controlled by the amount of poloidal magnetic flux threading the disk. The amount of magnetic flux must also coevolve with the disk, as a result of magnetic flux transport, a process that is poorly understood. In weakly ionized gas as in PPDs, magnetic flux is largely frozen in the electron fluid, except when resistivity is large. When the disk is largely laminar, we show that the relative drift between the electrons and ions (the Hall drift), and the ions and neutral fluids (ambipolar drift) can play a dominant role on the transport of magnetic flux. Using two-dimensional simulations that incorporate the Hall effect and ambipolar diffusion (AD) with prescribed diffusivities, we show that when large-scale poloidal field is aligned with disk rotation, the Hall effect rapidly drags magnetic flux inward at the midplane region, while it slowly pushes flux outward above/below the midplane. This leads to a highly radially elongated field configuration as a global manifestation of the Hall-shear instability. This field configuration further promotes rapid outward flux transport by AD at the midplane, leading to instability saturation. In quasi-steady state, magnetic flux is transported outward at approximately the same rate at all heights, and the rate is comparable to the Hall-free case. For anti-aligned field polarity, the Hall effect consistently transports magnetic flux outward, leading to a largely vertical field configuration in the midplane region. The field lines in the upper layer first bend radially inward and then outward to launch a disk wind. Overall, the net rate of outward flux transport is about twice as fast as that of the aligned case. In addition, the rate of flux transport increases with increasing disk magnetization. The absolute rate of transport is sensitive to disk microphysics, which remains to be explored in future studies.

A new approach to non-Abelian hydrodynamics

We present a new approach to describe hydrodynamics carrying non-Abelian macroscopic degrees of freedom. Based on the Kaluza-Klein compactification of a higher-dimensional neutral dissipative fluid on a manifold of non-Abelian isometry, we obtain a four-dimensional colored dissipative fluid coupled to Yang-Mills gauge field. We derive transport coefficients of resulting colored fluid, which feature non-Abelian character of color charges. In particular, we obtain color-specific terms in the gradient expansions and response quantities such as the conductivity matrix and the chemical potentials. We argue that our Kaluza-Klein approach provides a robust description of non-Abelian hydrodynamics, and discuss some links between this system and quark-gluon plasma and fluid/gravity duality.

Understanding fluid transport through the multiscale pore network of a natural shale

The pore structure of a natural shale is obtained by three imaging means. Micro-tomography results are extended to provide the spatial arrangement of the minerals and pores present at a voxel size of 700 nm (the macroscopic scale). FIB/SEM provides a 3D representation of the porous clay matrix on the so-called mesoscopic scale (10-20 nm); a connected pore network, devoid of cracks, is obtained for two samples out of five, while the pore network is connected through cracks for two other samples out of five. Transmission Electron Microscopy (TEM) is used to visualize the pore space with a typical pixel size of less than 1 nm and a porosity ranging from 0.12 to 0.25. On this scale, in the absence of 3D images, the pore structure is reconstructed by using a classical technique, which is based on truncated Gaussian fields. Permeability calculations are performed with the Lattice Boltzmann Method on the nanoscale, on the mesoscale, and on the combination of the two. Upscaling is finally done (by a finite volume approach) on the bigger macroscopic scale. Calculations show that, in the absence of cracks, the contribution of the nanoscale pore structure on the overall permeability is similar to that of the mesoscale. Complementarily, the macroscopic permeability is measured on a centimetric sample with a neutral fluid (ethanol). The upscaled permeability on the macroscopic scale is in good agreement with the experimental results.

Generation of deterministic eddy structure of the flow as an analogue of the phase transition of the second kind. Development of ideas of academician I.I. Novikov

The analysis of the physical processes leading to the structure formation of fluids has been done. The proposed theoretical approach can be used both for the neutral, conductive and magnetic fluids. In the present work the main attention is paid to the vortex and swirl flows of Newtonian fluids. Critical conditions accompanied the occurrence of hydrodynamic instabilities with a structural restructuring of flow field have been identified due to carried out physical experiments on generation of large-scale steady-stable vortex structures in channels of complicated geometry. Examples of topological models of the internal structure of the flow under condition of the phase transition of the second kind without changing of the aggregation state of the environment have been considered. It is shown that for vortex and swirl flows the parameter of helicity associated with the emergence of the internal angular momentum of the fluid and the structuring of the flow depending on the intensity of the local vorticity and orientation of longitudinal helical vortices can be accepted as the order parameter.

Parametric instabilities in shallow water magnetohydrodynamics of astrophysical plasma in external magnetic field

This article deals with magnetohydrodynamic (MHD) flows of a thin rotating layer of astrophysical plasma in external magnetic field. We use the shallow water approximation to describe thin rotating plasma layer with a free surface in a vertical external magnetic field. The MHD shallow water equations with external vertical magnetic field are revised by supplementing them with the equations that are consequences of the magnetic field divergence-free conditions and reveal the existence of third component of the magnetic field in such approximation providing its relation with the horizontal magnetic field. It is shown that the presence of a vertical magnetic field significantly changes the dynamics of the wave processes in astrophysical plasma compared to the neutral fluid and plasma layer in a toroidal magnetic field. The equations for the nonlinear wave packets interactions are derived using the asymptotic multiscale method. The equations for three magneto-Poincare waves interactions, for three magnetostrophic waves interactions, for the interactions of two magneto-Poincare waves and for one magnetostrophic wave and two magnetostrophic wave and one magneto-Poincare wave interactions are obtained. The existence of parametric decay and parametric amplifications is predicted. We found following four types of parametric decay instabilities: magneto-Poincare wave decays into two magneto-Poincare waves, magnetostrophic wave decays into two magnetostrophic waves, magneto-Poincare wave decays into one magneto-Poincare wave and one magnetostrophic wave, magnetostrophic wave decays into one magnetostrophic wave and one magneto-Poincare wave. Following mechanisms of parametric amplifications are found: parametric amplification of magneto-Poincare waves, parametric amplification of magnetostrophic waves, magneto-Poincare wave amplification in magnetostrophic wave presence and magnetostrophic wave amplification in magneto-Poincare wave presence. The instabilities growth rates are obtained respectively.

Eddy, drift wave and zonal flow dynamics in a linear magnetized plasma

Turbulence and its structure formation are universal in neutral fluids and in plasmas. Turbulence annihilates global structures but can organize flows and eddies. The mutual-interactions between flow and the eddy give basic insights into the understanding of non-equilibrium and nonlinear interaction by turbulence. In fusion plasma, clarifying structure formation by Drift-wave turbulence, driven by density gradients in magnetized plasma, is an important issue. Here, a new mutual-interaction among eddy, drift wave and flow in magnetized plasma is discovered. A two-dimensional solitary eddy, which is a perturbation with circumnavigating motion localized radially and azimuthally, is transiently organized in a drift wave – zonal flow (azimuthally symmetric band-like shear flows) system. The excitation of the eddy is synchronized with zonal perturbation. The organization of the eddy has substantial impact on the acceleration of zonal flow.

Multiple parallel assay operations with cross contamination avoidance in a given biochip

Digital microfluidic biochips are reforming many areas of biochemistry, biomedical sciences, as well as microelectronics. It is renowned as lab-on-a-chip for its appreciation as a substitute for laboratory experiments. Nowadays, for emergency purposes and to ensure cost efficacy, multiple assay operations are essential to be carried out simultaneously. In this context, parallelism is of utmost importance in designing biochip while the size of a chip is a constraint. Hence, the objective of this study is to enhance the performance of a chip in terms of its throughput, electrode utilisation, and pin count as well. Here, the authors have considered some of the most familiar assay requirements where a sample is to be analysed using different reagents, and identify some parameter(s) of the sample(s) under consideration. Moreover, sample preparation is a vital task in digital microfluidic biochip; thus, dilution of different samples up to different concentrations using buffer (neutral) fluid is a crucial issue. In this design, the authors effectively perform this task in parallel in a number of sub-regions of a given restricted sized chip using an array based partitioning pin-assignment technique while taking care of the cross contamination problem. The design has been verified for some significant real life assay examples.

Effects of radial electric field on suppression of electron-temperature-gradient mode through multiscale nonlinear interactions

Turbulence in fluids and plasmas is ubiquitous in Nature and in the laboratory. Contrary to the importance of the ‘scale-free’ nature of cascade in neutral fluid turbulence, the turbulence in plasma is characterised by dynamics of distinct length scales. The cross-scale interactions can be highly non-symmetric so as to generate the plasma turbulence structures. Here we report that the system of hyper-fine electron-temperature-gradient (ETG) fluctuations and microscopic drift-wave (DW) fluctuations is strongly influenced by the sign of the gradient of the radial electric field through multiscale nonlinear interactions. The selective suppression effects by radial electric field inhomogeneity on DW mode induce a new route to modify ETG mode. This suppression mechanism shows disparity with respect to the sign of the radial electric field inhomogeneity, which can be driven by turbulence, so that it could be a new source for symmetry breaking in the turbulence structure formation in plasmas.

The Borinquen geothermal system (Cañas Dulces caldera, Costa Rica)

The geotectonic location of Costa Rica has allowed the development of an active volcanic arc, geological context associated with hydrothermal systems with geothermal potential. In the northwest of the country, on the Pacific slope of the Rincon de la Vieja volcano, inside the Cañas Dulces caldera, the presence of thermal manifestations motivated the development of geoscientific studies that culminated with the drilling of 4 geothermal exploration wells to depths of 2078–2594m, as part of the research that seeks to corroborate the existence of a commercially geothermal reservoir. A date has explored an area of 31km2 known as Borinquen where information on lithostratigraphy, mineralogy, electric resistivity and thermal gradients, as well as on the geochemical and isotopic composition of the fluids derived from the meteoric water, surface hydrothermal manifestation and exploration wells, was obtained. The distribution of the secondary mineral assemblages observed in the exploration wells suggests an increase in temperature with depth, which is confirmed by the distribution of the thermal gradient. The geoelectric structure hints at the existence of a cap rock and a geothermal reservoir, and the geochemistry and isotopic composition of the samples obtained from the exploration wells reveal the existence of neutral sodium chloride fluids with high enthalpy. This suggests exploitation could be economically viable, particularly in light of comparisons with similar reservoirs already being exploited in the neighbouring calderas of San Vicente and Guayabo. Taking into account all the available information, we provide a conceptual model of the Borinquen geothermal area that explains the main elements of its high enthalpy geothermal system – heat source, distribution of the thermal anomaly, recharge zone, reservoir, cap rock, main flow paths and flow directions. This will be useful as a guide for the exploration and future development and exploitation of this geothermal resource.

Interchange Turbulence Model for the Edge Plasma in SOLEDGE2D‐EIRENE

AbstractCross‐field transport in edge tokamak plasmas is known to be dominated by turbulent transport. A dedicated effort has been made to simulate this turbulent transport from first principle models but the numerical cost to run these simulations on the ITER scale remains prohibitive. Edge plasma transport study relies mostly nowadays on so‐called transport codes where the turbulent transport is taken into account using effective ad‐hoc diffusion coeffecients. In this contribution, we propose to introduce a transport equation for the turbulence intensity in SOLEDGE2D‐EIRENE to describe the interchange turbulence properties. Going beyond the empirical diffusive model, this system automatically generates profiles for the turbulent transport and hence reduces the number of degrees of freedom for edge plasma transport codes. We draw inspiration from the k‐epsilon model widely used in the neutral fluid community. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

The role of Alfvén wave heating in solar prominences

Observations have shown that magnetohydrodynamic waves over a large frequency range are ubiquitous in solar prominences. The waves are probably driven by photospheric motions and may transport energy up to prominences suspended in the corona. Dissipation of wave energy can lead to heating of the cool prominence plasma, so contributing to the local energy balance within the prominence. Here we discuss the role of Alfv\'en wave dissipation as a heating mechanism for the prominence plasma. We consider a slab-like quiescent prominence model with a transverse magnetic field embedded in the solar corona. The prominence medium is modelled as a partially ionized plasma composed of a charged ion-electron single fluid and two separate neutral fluids corresponding to neutral hydrogen and neutral helium. Friction between the three fluids acts as a dissipative mechanism for the waves. The heating caused by externally-driven Alfv\'en waves incident on the prominence slab is analytically explored. We find that the dense prominence slab acts as a resonant cavity for the waves. The fraction of incident wave energy that is channelled into the slab strongly depends upon the wave period, $P$. Using typical prominence conditions, we obtain that wave energy trapping and associated heating are negligible when $P \gtrsim 100$ s, so that it is unlikely that those waves have a relevant influence on prominence energetics. When $1$ s $\lesssim P \lesssim 100$ s the energy absorption into the slab shows several sharp and narrow peaks, that can reach up to 100%, when the incident wave frequency matches a cavity resonance of the slab. Wave heating is enhanced at those resonant frequencies. Conversely, when $P \lesssim 1$ s cavity resonances are absent, but the waves are heavily damped by the strong dissipation. We estimate that wave heating may compensate for about 10% of radiative losses of the prominence plasma.

The formation and evolution of reconnection-driven, slow-mode shocks in a partially ionised plasma

The role of slow-mode MHD shocks in magnetic reconnection is one of great importance for energy conversion and transport, but in many astrophysical plasmas the plasma is not fully ionised. In this paper, we investigate, using numerical simulations, the role of collisional coupling between a proton-electron charge-neutral fluid and a neutral hydrogen fluid for the 1D Riemann problem initiated in a constant pressure and density background state by a discontinuity in the magnetic field. This system, in the MHD limit, is characterised by two waves: a fast-mode rarefaction wave that drives a flow towards a slow-mode MHD shock. The system evolves through four stage: initiation, weak coupling, intermediate coupling and a quasi steady state. The initial stages are characterised by an over-pressured neutral region that expands with characteristics of a blast wave. In the later stages, the system tends towards a self-similar solution where the main drift velocity is concentrated in the thin region of the shock front. Due to the nature of the system, the neutral fluid is overpressured by the shock when compared to a purely hydrodynamic shock which results in the neutral fluid expanding to form the shock precursor. The thickness of the shockfront once it has formed proportional to the ionisation fraction to the power -1.2, which is a smaller exponent than would be naively expected from simple scaling arguments. One interesting result is that the shock front is a continuous transition of the physical variables for sub-sonic velocity upstream of the shock front (a c-shock) to a sharp jump in the physical variables followed by a relaxation to the downstream values for supersonic upstream velocity (a j-shock). The frictional heating that results from the velocity drift across the shock front can amount to approximately two per cent of the reference magnetic energy.

A magnetite-rich Cyprus-type VMS deposit in Ortaklar: A unique VMS style in the Tethyan metallogenic belt, Gaziantep, Turkey

The Ortaklar VMS deposit is hosted in the Koçali Complex consisting of basalts and deep sea pelagic sediments, which formed by rifting and continental break-up of the southern Neotethyan in Late Triassic. The basalts are of NMORB-type without notable crustal contamination. From the surface to depth, the Ortaklar deposit consists of a gossan zone, a thick massive ore zone and a poorly developed stockwork zone. Primary mineralisation is characterised by distinctive facies including sulphide breccias (proximal), graded beds (distal), stockworks and chimney fragments. Ore mineral abundances decrease in the order of pyrite, magnetite, chalcopyrite, and sphalerite. Two distinct phases of mineralisation, massive magnetite and massive sulphide, are present in the Ortaklar deposit. Textural evidence (e.g., magnetite replacing sulphides) and the spatial relationships with the host rocks indicate that magnetite and sulphide minerals were generated in different stages. The transition from sulphide to magnetite mineralisation is interpreted to relate to variation in H2S content of ore fluids. The 1st stage massive sulphide ore might have formed by early hydrothermal fluids rich in Fe and H2S. The 2nd stage massive magnetite might have formed by later neutral hydrothermal fluids rich in Fe but poor in H2S, replacing the pre-existing sulphide ore.The alteration patterns, mineral paragenesis, lithological features (massive ore-stockwork ore-gossan) of the Ortaklar deposit together with its trace elements, Cu-Pb-Zn-Au-Ag and REE signatures are all consistent with a Cyprus-type VMS system. The δ34S values in pyrite and chalcopyrite samples range from 2.6 to 5.7‰, indicating that the hydrothermal fluids were associated with sub-seafloor igneous activity, typical of Cyprus-type VMS deposits. However, magnetite formed later than sulphide minerals in the Ortaklar deposit, contrasting with typical Cyprus-type VMS deposits where magnetite generally occurs in lower sections. Consequently, although the Ortaklar deposit generally conforms to Cyprus-type deposits, it is distinguished from them by its late stage and high magnetite concentration. Thus, the Ortaklar deposit is thought to be an exceptional and perhaps unique Cyprus-type VMS deposit.

Computational challenges in magnetic-confinement fusion physics

Magnetic-fusion plasmas are complex self-organized systems with an extremely wide range of spatial and temporal scales, from the electron-orbit scales (∼10−11 s, ∼ 10−5 m) to the diffusion time of electrical current through the plasma (∼102 s) and the distance along the magnetic field between two solid surfaces in the region that determines the plasma–wall interactions (∼100 m). The description of the individual phenomena and of the nonlinear coupling between them involves a hierarchy of models, which, when applied to realistic configurations, require the most advanced numerical techniques and algorithms and the use of state-of-the-art high-performance computers. The common thread of such models resides in the fact that the plasma components are at the same time sources of electromagnetic fields, via the charge and current densities that they generate, and subject to the action of electromagnetic fields. This leads to a wide variety of plasma modes of oscillations that resonate with the particle or fluid motion and makes the plasma dynamics much richer than that of conventional, neutral fluids. Simulating magnetically confined fusion plasmas is crucial to understand and control them. Here, the state of the art and the multi-physics involved are discussed: electromagnetism and hydrodynamics combined over vast spatiotemporal ranges.