Presence Of Weak Magnetic Field Research Articles

Momentum transport properties of a hot and dense QCD matter in a weak magnetic field

We have studied the momentum transport properties of a hot and dense QCD matter in the presence of weak magnetic field by determining the shear (eta ) and bulk (zeta ) viscosities in the relaxation time approximation of kinetic theory. The dependence of eta and zeta on the temperature has been explored in the presence of weak magnetic field (B-field) and finite chemical potential (mu ). It is observed that both shear and bulk viscosities get decreased in the presence of a weak magnetic field, whereas the finite chemical potential increases these viscosities, specifically at low temperatures. This study is important to understand the sound attenuation through the Prandtl number (Pr), the nature of the flow through the Reynolds number (Re), the fluidity and location of transition point of the matter through the ratios eta /s and zeta /s (s is the entropy density), respectively. The Prandtl number is observed to increase in the weak magnetic field, whereas the presence of a finite chemical potential reduces its magnitude as compared to the scenario of absence of B-field and mu . However, Pr still remains larger than unity, indicating that the energy dissipation due to the sound attenuation is mostly governed by the momentum diffusion. It is noticed that the weak magnetic field makes the Reynolds number larger, whereas the chemical potential makes it smaller than that in the absence of B-field and mu . We have observed that the ratio eta /s decreases in the weak magnetic field regime, whereas the finite chemical potential increases its value, but the ratio zeta /s is found to decrease in the presence of weak magnetic field as well as finite chemical potential.

MANIFESTATION IN IR-LUMINESCENCE OF THE CROSS RELAXATION PROCESSES BETWEEN NV CENTERS IN WEAK MAGNETIC FIELDS

We present a combined experimental and theoretical study of the effect of magnetic field on the luminescence from an ensemble of NV centers in diamond. It was found that the intensity of infrared luminescence associated with transitions between singlet levels of NV centers shows a pronounced increase of a near-zero magnetic field. The influence of the power and polarization of laser radiation on the amplitude and shape of the revealed local maximum in IR-luminescence of NV centers is investigated. An eight-level photophysical model of an NV center in the presence of an arbitrarily directed magnetic field has been constructed
 and on its basis the calculation has been performed of the luminescence intensity emitted by an ensemble of NV center, both in the visible and infrared regions of the spectrum. It is shown that the phenomenological allowance for the cross-relaxation of NV centers between each other and with other paramagnetic
 centers in a diamond within the framework of this model allows describing the experimentally observed fluorescence features of an ensemble of NV centers in the presence of weak magnetic fields.

Dynamics of flow reversals in the presence of a vertical magnetic field (a) (a)Contribution to the Focus Issue Turbulent Thermal Convection edited by Mahendra Verma and Jörg Schumacher.

We investigate the dynamics of flow reversals close to the onset of Rayleigh-Bénard convection (RBC) of electrically conducting low Prandtl number (Pr) Boussinesq fluids in the presence of an external vertical magnetic field. The investigation is carried out by performing three-dimensional (3D) direct numerical simulations (DNS) of the related mathematical model considering the quasi-static approximation. The numerical investigation reveals a rich dynamics of the flow reversals close to the onset of convection. Three qualitatively different kinds of flow reversals, namely chaotic, intermittent and periodic are identified and all are found to occur in the presence of weak magnetic field, measured in terms of the Chandrasekhar number (Q). Explored ranges of the Prandtl number (Pr), the Rayleigh number (Ra) and the Chandrasekhar number are , and , respectively. Out of the three different types of flow reversals, intermittent flow reversal is new and has not been reported so far in convective system to the best of our knowledge. The probability density function of the time interval of occurrences of chaotic flow reversals is found to decay exponentially. The heat transfer properties of the system are also numerically investigated and it is observed that magnetic field facilitates the heat transfer in the considered ranges of the parameter space.

Adsorption of Sb(III) from Aqueous Solution by nZVI/AC: A Magnetic Fixed-Bed Column Study.

The effectiveness of nanoscale zero-valent iron(nZVI) immobilized on activated carbon (nZVI/AC) in removing antimonite (Sb(III)) from simulated contaminated water was investigated with and without a magnetic fix-bed column reactor. The experiments were all conducted in fixed-bed columns. A weak magnetic field (WMF) was proposed to increase the exclusion of paramagnetic Sb(III) ions by nZVI/AC. The Sb(III) adsorption to the nZVI and AC surfaces, as well as the transformation of Sb(III) to Sb(V) by them, were both increased by using a WMF in nZVI/AC. The increased sequestration of Sb(III) by nZVI/AC in the presence of WMF was followed by faster nZVI corrosion and dissolution. Experiments were conducted as a function of the pH of the feed solution (pH 5.0–9.0), liquid flow rate (5–15 mL·min−1), starting Sb(III) concentration (0.5–1.5 mg·L−1), bed height nZVI/AC (10–40 cm), and starting Sb(III) concentration (0.5–1.5 mg·L−1). By analyzing the breakthrough curves generated by different flow rates, different pH values, different inlet Sb(III) concentrations, and different bed heights, the adsorbed amounts, equilibrium nZVI uptakes, and total Sb(III) removal percentage were calculated in relation to effluent volumes. At pH 5.0, the longest nZVI breakthrough time and maximal Sb(III) adsorption were achieved. The findings revealed that the column performed effectively at the lowest flow rate. With increasing bed height, column bed capacity and exhaustion time increased as well. Increasing the Sb(III) initial concentration from 0.5 to 1.5 mg·L−1 resulted in the rise of adsorption bed capacity from 3.45 to 6.33 mg·g−1.

Role of weak magnetic field for enhanced oxidation of orange G by magnetic Fenton.

The role of weak magnetic field (WMF) on the degradation of a common textile azo-dye, orange G (OG), by magnetic Fenton system was investigated in detail. The results showed that the presence of WMF can provide better performance of the Fe3O4/H2O2 system for OG degradation. The optimized reaction conditions were contained at 1 mM Fe3O4 as Fe, 20 mT of magnetic field intensity, 20 mM H2O2, and initial pH of 3.0. The removal efficiency of OG by Fe3O4/H2O2 coupling with WMF increased largely from 56.3 to 82.3% compared with Fe3O4/H2O2 process. Both the electron paramagnetic resonance (EPR) analysis and the quenching effect of tert-butyl alcohol (TBA) confirmed that hydroxyl radical (•OH) was the primary reactive oxygen species in WMF-Fe3O4/H2O2 system. The improving effect of WMF was explained by the magnetoconvection theory. The presence of WMF could accelerate the corrosion rate of Fe3O4 and thus promoted the release of Fe(II), which led to the increased production of •OH and enhanced the degradation of OG. Moreover, it was surprising to observe that the WMF induced improvement in OG degradation by heterogeneous Fenton involving the iron sludge, namely FeOOH and Fe2O3, as catalysts. These results indicated that WMF could be utilized as an efficient and cost-effective strategy to improve the removal of organic pollutants by iron oxide-based Fenton process.

Sensitivity of PS/CoPd Janus particles to an external magnetic field.

The dual nature of Janus particles confers fascinating properties such as a response to multiple stimuli. In this communication, we systematically study the sensitivity to a uniform external magnetic field of isolated Janus rod-shaped and spherical particles in water confined to two dimensions. The Janus asymmetry of the particles is given by magnetic [Co(0.28 nm)/Pd(0.90 nm)]8 multilayer films deposited onto monodisperse polystyrene (PS) nanorods and microspheres, respectively. It is shown that the particles dispersed in water respond to weak magnetic field applied in in-plane direction. Here we demonstrate that a precise control of the in-plane particle orientation can be obtained for magnetic field strengths higher than 0.1 mT for microspheres and 0.4 mT for nanorods.

Polyelectrolyte-based magnetic photonic crystals with anticoagulant activity

Magnetic photonic crystals are an emerging class of responsive colloidal systems with unique variable optical properties. This article is dedicated to the first example of polyelectrolyte-based magnetic photonic crystals produced by layer-by-layer adsorption of polymeric molecules onto magnetite cores. Proper selection of the polycationic and polyanionic molecules allowed to produce a stable colloidal system composed of monodisperse nanoaggregates with a mean diameter of 180 nm. In the presence of weak magnetic fields up to 650 G, the reflectance spectra of the colloid system showed a blue shift, changing spectra peak maximum from 720 to 445 nm. Mild synthetic conditions allowed to use natural polymers, such as heparin, expanding the bioactivity of the produced material. Magnetic photonic crystals have demonstrated excellent biocompatibility with minor cytotoxicity on HeLa cell line up to 200 μg/mL concentration, and anticoagulant activity comparable to free heparin. The synthesized material can find its application in the fields of optics, biosensorics, or biocompatible magnetic drug delivery systems for anticoagulant therapy.

Dynamical behaviour of non‐linear quantum ion acoustic wave in weakly magnetized electron–positron–ion plasma

AbstractIn order to investigate the propagation characteristics of linear and non‐linear ion acoustic waves (IAWs) in electron–positron–ion quantum plasma in the presence of external weak magnetic field, we have used a quantum hydrodynamic model, and degenerate statistics for the electrons and positrons are taken into account. It is found that the linear dispersion relation of the IAW was modified by the externally applied magnetic field. By using the reductive perturbation technique, a gyration‐modified Korteweg‐de Vries equation is derived for finite amplitude non‐linear IAWs. Time‐dependent numerical simulation shows the formation of an oscillating tail in front of the ion acoustic solitons in the presence of a weak magnetic field. It is also seen that the amplitude and width of solitons and oscillating tails are affected by the relevant plasma parameters such as quantum diffraction, positron concentration, and magnetic field. We have performed our analysis by extending it to account for approximate soliton solution by asymptotic perturbation technique and non‐linear analysis via a dynamical system approach. The analytical results show the distortion of the shape of the localized soliton with time, and the non‐linear analysis confirms the generation of oscillating tails.

Magnetic and thermodynamic properties of the octanuclear nickel phosphonate-based cage

We report a detailed theoretical investigation into the influence of anisotropy on the magnetic and thermodynamic properties of an octanuclear nickel phosphonate cage with butterfly-shaped molecular geometry, namely Ni8(μ3−OH)4(OMe)2(O3PR1)2(O2CtBu)6(HO2CtBu)8. To validate our exact diagonalization approach, we firstly compare results with simulations and experiment in the isotropic case. Having established concurrence, we then introduce uniaxial single-ion anisotropy and Heisenberg exchange anisotropy between interacted nickel atoms. We then examine effects of both anisotropy parameters on the magnetization process, as well as on the specific heat of the model. We predict intermediate magnetization plateaus, including zero plateau, and magnetization jumps with magnetic ground-state phase transitions at low temperature T=1 K. The magnetization plateaus are strongly dependent on both the levels of exchange anisotropy and single-ion anisotropy. Varying the former leads to change in width and magnetic position of all intermediate plateaus while they become wider upon increasing the latter. The specific heat of the model manifests a Schottky-type maximum at moderate temperature in the presence of weak magnetic fields, when the system is isotropic. The introduction of anisotropy results in substantial variations in the thermal behavior of the specific heat. Indeed, by tuning anisotropy parameters the Schottky peak convert to a double-peak temperature dependence that coincided with the magnetization jumps. We call for these theoretical predictions to be verified experimentally at low temperature.

Alignment of s -state Rydberg molecules in magnetic fields

We unravel some peculiar properties of ultralong-range Rydberg molecules formed by an $s$-state $^{87}$Rb Rydberg atom and a corresponding ground-state atom whose electronic orbitals are spherically symmetric and therefore should not be influenced by the presence of weak magnetic fields. However, the electron-atom interaction, which establishes the molecular bond, is under certain conditions subject to a sizeable spin-orbit coupling and, hence, sensitive to the magnetic field. This mechanism can be harnessed to counterintuitively align the $s$-state molecules with respect to the field axis. We demonstrate this by analyzing the angular-dependent Born-Oppenheimer potential energy surfaces and the supported vibrational molecular states. Our predictions open novel possibilities to access the physics of relativistic electron-atom scattering experimentally.

Convective cells in Betelgeuse: imaging through spectropolarimetry

Aims. We assess the ability to image the photosphere of red supergiants and, in particular Betelgeuse, through the modelling of the observed linear polarization in atomic spectral lines. We also aim to analyse the resulting images over time, to measure the size and dynamics of the convective structures in these stars. Methods. Rayleigh scattering polarizes the continuum and spectral lines depolarize it. This depolarization is seen as a linear polarization signal parallel to the radial direction on the stellar disk. Integrated over the disk, it would result in a null signal, except if brightness asymmetries/inhomogeneities are present. This is the basic concept behind our imaging technique. Through several tests and comparisons, we have tried to assess and extend its validity, and to determine what can be learnt unambiguously through it. Results. The several tests and comparisons performed prove that our technique reliably retrieves the salient brightness structures in the photosphere of Betelgeuse, and should be relevant to other red supergiants. For Betelgeuse, we demonstrate that these structures we infer are convective cells, with a characteristic size of more than 60% of the stellar radius. We also derive the characteristic upflow and downflow speeds, 22 and 10 km s−1, respectively. We find weak magnetic fields concentrated in the downflow lanes in between granules, similar to the quiet sun magnetism. We follow those convective structures in time. Changes happen on timescales of 1 week, but individual structures can be tracked over 4 yr of observations. Conclusions. The measured characteristics of the convection in Betelgeuse confirm the predictions of numerical simulations in both the strong, supersonic upflows and the size of the convective cells. They also concur in the presence of weak magnetic fields that are completely dominated by the convective flows and constrained to the dark lanes of down-flowing plasma.

Weak magnetic field for enhanced oxidation of sulfamethoxazole by Fe0/H2O2 and Fe0/persulfate: Performance, mechanisms, and degradation pathways

In this study, effects of the nonuniform weak magnetic field (WMF) on sulfamethoxazole (SMX) degradation rate by H2O2 and persulfate (PS) coupled with different zero-valent iron (Fe0) samples were investigated. The kobs value (pseudo-first-order rate constant) of SMX degradation by Fe0/H2O2 or Fe0/PS was accelerated by WMF irradiation. Meanwhile, the release rate of dissolved iron was increased in the presence of WMF which indicated WMF irradiation could promote Fe0 corrosion in Fe0/H2O2 and Fe0/PS systems. Effects of WMF on SMX degradation kinetics by Fe0/H2O2 or Fe0/PS in the initial system pH (pHini) range of 3.0–7.0 were studied. Although WMF accelerated SMX removal by Fe0/H2O2 at pHini 3.0 and 4.0, WMF did not exhibit advantages at higher pHini. In Fe0/PS systems, WMF could promote SMX removal during the investigated pH range of 3.0–7.0, and kobs of SMX removal depended on the form of aquatic SMX which suggested that SO4− could selectively degrade dissociated or protonated SMX. Although SO42−, Cl−, and NO3− showed different effects on SMX degradation by Fe0/H2O2 or Fe0/PS, WMF could accelerate SMX degradation in the presence of these common anions. Chemical quenching experiments and electron paramagnetic resonance (EPR) studies identified that main reactive oxygen species (ROS) generated in Fe0/H2O2/WMF and Fe0/PS/WMF systems were OH and SO4−, respectively. Meanwhile, the detection of ROS proved that WMF did not change the type of ROS in Fe0/H2O2 or Fe0/PS systems. Finally, degradation pathways of SMX by Fe0/H2O2/WMF and Fe0/PS/WMF were proposed based on transformation products.

Adhesion of gram-negative rod-shaped bacteria on 1D nano-ripple glass pattern in weak magnetic fields.

This research project has major applications in the healthcare and biomedical industries. Bacteria reside in human bodies and play an integral role in the mechanism of life. However, their excessive growth or the invasion of similar agents can be dangerous and may cause fatal or incurable diseases. On the other hand, increased exposure to electromagnetic radiation and its impact on health and safety is a common concern to medical science. Some nanostructure materials have interesting properties regarding facilitating or impeding cell growth. An understanding of these phenomena can be utilized to establish the optimum benefit of these structures in healthcare and medical research. We focus on the commonly found rod‐shaped, gram‐negative bacteria and their orientation and community development on the cellular level in the presence of weak magnetic fields on one dimensional nano‐ripple glass patterns to investigate the impact of nanostructures on the growth pattern of bacteria. The change in bacterial behavior on nanostructures and the impact of magnetic fields will open up new venues in the utilization of nanostructures. It is noticed that bacterial entrapment in nano‐grooves leads to the growth of larger colonies on the nanostructures, whereas magnetic fields reduce the size of colonies and suppress their growth.

Effect of Weak Magnetic Field on Bacterial Growth

Effects of weak magnetic fields are observed on the growth of various bacterial strains. Different sources of a constant magnetic field are used to demonstrate that ion transport in the nutrient broth and bacterial cellular dynamics is perturbed in the presence of weak magnetic field which affects the mobility and absorption of nutrients in cells and hence their doubling rate. The change is obvious after a few hours of exposure and keeps on increasing with time for all the observed species. The growth rate depends on the field strength and the nature of the magnetic field. The field effect varies with the shape and the structure of the bacterial cell wall as well as the concentration of nutrient broth. We closely study the growth of three species Escherichia coli, Pseudomonas aeruginosa and Staphylococcus epidermidis with the same initial concentrations at the same temperature in the same laboratory environment. Our results indicate that the weak static field of a few gauss after a few hours gives a measurable change in the growth rates of all bacterial species. This shows that the same magnetic field has different effects on different species in the same environment.

Zero Prandtl-number rotating magnetoconvection

We investigate instabilities and chaos near the onset of Rayleigh-Bénard convection of electrically conducting fluids with free-slip, perfectly electrically and thermally conducting boundary conditions in the presence of uniform rotation about the vertical axis and horizontal external magnetic field by considering zero Prandtl-number limit (Pr → 0). Direct numerical simulations (DNSs) and low-dimensional modeling of the system are done for the investigation. Values of the Chandrasekhar number (Q) and the Taylor number (Ta) are varied in the range 0 < Q, Ta ≤ 50. Depending on the values of the parameters in the chosen range and the choice of initial conditions, the onset of convection is found be either periodic or chaotic. Interestingly, it is found that chaos at the onset can occur through four different routes, namely, homoclinic, intermittent, period doubling, and quasiperiodic routes. Homoclinic and intermittent routes to chaos at the onset occur in the presence of weak magnetic field (Q < 2), while the period doubling route is observed for relatively stronger magnetic field (Q ≥ 2) for one set of initial conditions. On the other hand, the quasiperiodic route to chaos at the onset is observed for another set of initial conditions. However, the rotation rate (value of Ta) also plays an important role in determining the nature of convection at the onset. Analysis of the system simultaneously with DNSs and low-dimensional modeling helps us to clearly identify different flow regimes concentrated near the onset of convection and understand their origins. The periodic or chaotic convection at the onset is found to be connected with rich bifurcation structures involving subcritical pitchfork, imperfect pitchfork, supercritical Hopf, imperfect homoclinic gluing, and Neimark-Sacker bifurcations.

Influence of weak magnetic field and tartrate on the oxidation and sequestration of Sb(III) by zerovalent iron: Batch and semi-continuous flow study

The influence of weak magnetic field (WMF) and tartrate on the oxidation and sequestration of Sb(III) by zerovalent iron (ZVI) was investigated with batch and semi-continuous reactors. The species analysis of antinomy in aqueous solution and solid precipitates implied that both Sb(III) adsorption preceding its conversion to Sb(V) in solid phase and Sb(III) oxidation to Sb(V) preceding its adsorption in aqueous phase occurred in the process of Sb(III) sequestration by ZVI. The application of WMF greatly increased the rate constants of Sbtot (total Sb) and Sb(III) disappearance during Sb(III)-tartrate and uncomplexed-Sb(III) sequestration by ZVI. The enhancing effect of WMF was primarily due to the accelerated ZVI corrosion in the presence of WMF, as evidenced by the influence of WMF on the change of solution and solid properties with reaction. However, tartrate greatly retarded Sb removal by ZVI. It was because tartrate inhibited ZVI corrosion, competed with Sb(III) and Sb(V) for the active surface sites, increased the negative surface charge of the generated iron (hydr)oxides due to its adsorption, and formed soluble complexes with Fe(III). The positive effect of WMF on Sb(III)-tartrate and uncomplexed-Sb(III) removal by ZVI was also verified with a magnetic semi-continuous reactor.

Long-range spin correlations in a honeycomb spin model with a magnetic field

We consider spin-$\frac{1}{2}$ model on the honeycomb lattice in the presence of weak magnetic field $h\ll J$. Such a perturbation treated in the second order over $h$ leads to the power-law decay of irreducible spin correlation function $S(\mathbf{r},t)=\left\langle \left\langle s^{z}_r(t)s^{z}_0(0)\right\rangle \right\rangle \propto h_{z}^{2}f(t,\mathbf{r})$, where $f(t,\mathbf{r})\propto \lbrack \max (t,Jr)]^{-4}$ is an oscillating function of $\mathbf{r}$, with a wavelength equal to 3 lattice constants. In the present Letter we sum main terms in all orders of the perturbation theory for the correlation function $S(\mathbf{r},t)$ in the limit of large $r,t$. Our results can be understood in terms of the effective low-energy Hamiltonian written in terms of Majorana fermions, which in the presence of magnetic field acquire vector potential $A_x \propto h_z^2$. Correspondingly, the wave vector of the oscillations in $S(\mathbf{r},t)$ changes according to $\delta k \propto h_z^2$. We also compute the dynamic structure factor $S(\mathbf{p},\omega)$; in the vicinity of $\mathbf{p}_K$ corresponding to the inter-conical points excitations it reads as $S(\mathbf{p},\omega)-S(\mathbf{p}_K,\omega)\propto\sqrt{\omega^2-3J^2(\mathbf{p}-\mathbf{p}_K)^2}$.

Efficient selenate removal by zero-valent iron in the presence of weak magnetic field

Abstract Se(VI) was very refractory to be removed by zero-valent iron (ZVI), therefore weak magnetic field (WMF) was employed to achieve efficient Se(VI) removal by ZVI. Batch experiments showed that negligible Se(VI) ( −1 Se(VI) was achieved by ZVI in 90 min. The main portion of kinetics of Se(VI) removal by ZVI in the presence of WMF followed zero-order rate law and the rate constants of Se(VI) sequestration by ZVI increased progressively with increasing the ZVI dosage. Fe K -edge XAFS spectra and synchrotron radiation-XRD analysis revealed that ZVI was transformed to X-ray amorphous Fe 3 O 4 before finally transformed to lepidocrocite (γ-FeOOH). The LCF analysis of Se K -edge XANES spectra indicated that adsorptive removal of Se(VI) was minor but adsorption of Se(VI) to the corroded ZVI surface was the first step of Se(VI) removal. Se(VI) was rapidly reduced to Se(IV), which could be further transformed to Se(0). Comparison of the performance of Se(VI) removal in the literature suggested that employing WMF to enhance Se(VI) removal by ZVI under oxic conditions be a promising method.

CHROMOSPHERIC POLARIZATION IN THE PHOTOSPHERIC SOLAR OXYGEN INFRARED TRIPLET

We present multilevel radiative transfer modeling of the scattering polarization observed in the solar O I infrared triplet around 777 nm. We demonstrate that the scattering polarization pattern observed on the solar disk forms in the chromosphere, far above the photospheric region where the bulk of the emergent intensity profiles originates. We study the sensitivity of the polarization pattern to the thermal structure of the solar atmosphere and to the presence of weak magnetic fields (0.01 - 100 G) through the Hanle effect, showing that the scattering polarization signals of the oxygen infrared triplet encode information on the magnetism of the solar chromosphere.

Detecting the presence of weak magnetic fields using nitrogen-vacancy centers

We show how nitrogen-vacancy centers can be used to detect the presence of weak magnetic fields, that is, to find out whether a magnetic field, about which we may not have complete information, is actually present or not. The solution to this problem comes from quantum state discrimination theory. The effect of decoherence is taken into account to optimize the time over which the nitrogen-vacancy center is allowed to interact with the magnetic field before making a measurement. We also find the optimum measurement that should be performed. We then show how multiple measurements reduce the error in detecting the magnetic field. Finally, a major limitation of the measurement process, namely, limited photon detection efficiency, is taken into account. Our proposals should be implementable with current experimental technology.