Significant Effect Of Magnetic Field Research Articles

Thermal characterization of hybrid nanofluid with impact of convective boundary layer flow and Joule heating law: Dual solutions case study

This study emphasizes the dual exposition of the impact of convective condition and the significant effects of magnetic field, heat source and velocity slip on hybrid nanofluid flow over the exponentially shrinking sheet. The hybrid nanofluid is regarded as a contemporary variety of nanofluid; consequently, it is utilized to enhance the efficiency of heat transfer. By applying the Tiwari–Das model, the key objective of the current research is to investigate the impact of involving factors Biot number, Eckert number, volume fraction, magnetohydrodynamic (MHD), slip and suction on the temperature and velocity profiles. In addition, the Nusselt number and skin friction variations have been explored against the suction effect on the solid volume fraction of copper [Formula: see text] [1–3%] and the Biot number [Formula: see text] [1–3%]. The nonlinear partial differential equations are converted to a set of an ordinary differential equations by incorporating exponential similarity vectors. Eventually, ordinary differential equations are rectified utilizing MATLAB bvp4c solver. The results demonstrate the presence of dual exposition for suction with varying values of copper volume fraction and the Biot number. The heat transmission rate is observed to escalate in both cases as the strength of the Biot and Eckert numbers intensifies in the range of 1–3%. In summary, the results show that duality and non-unique solutions occur in the aiding flow situation when the suction [Formula: see text], while there is no flow and unique solutions of hybrid nanofluid feasible when [Formula: see text].

Magnetic-Field-Induced Sign Changes of Thermal Expansion in DyCrO4

The anharmonicity of lattice vibration is mainly responsible for the coefficient of thermal expansion (CTE) of materials. External stimuli, such as magnetic and electric fields, thus cannot effectively change the CTE, much less the sign variation from positive to negative or vice versa. In this study, we report significant magnetic field effects on the CTE of zircon- and scheelite-type DyCrO4 prepared at ambient and high pressures, respectively. At zero field, the zircon-type DyCrO4 exhibits a negative CTE below the ferromagnetic-order temperature of 23 K. With increasing field up to ≥1.0 T, however, the sign of the CTE changes from negative to positive. In the scheelite phase, magnetic field can change the initially positive CTE to be negative with a field up to 2.0 T, and then a reentrant positive CTE is induced by enhanced fields ≥3.5 T. Both zircon and scheelite phases exhibit considerable magnetostrictive effects with the absolute values as high as ∼ 800 ppm at 2 K and 10 T. The strong spin–lattice coupling is discussed to understand the unprecedented sign changes of the CTE caused by applying magnetic fields. The current DyCrO4 provides the first example of field-induced sign change of thermal expansion, opening up a way to readily control the thermal expansion beyond the conventional chemical substitution.

Spin-Enhanced C–C Coupling in CO 2 Electroreduction with Oxide-Derived Copper

Spin-Enhanced C–C Coupling in CO ₂ Electroreduction with Oxide-Derived Copper

Experimental measurement of ionization chamber angular response and associated magnetic field correction factors in MR-linac.

To measure ionization chamber dose response as a function of the angle between magnetic field direction and ionization chamber orientation in magnetic resonance-guided radiation therapy (MRgRT) system, and to evaluate angular dependence of magnetic field correction factor for reference dosimetry. Measurements were performed on an Elekta MR-linac that integrates a 1.5-T Philips MRI and a 7-MV FFF photon beam accelerator. The response of four reference class chambers (Exradin-A19, A1SL, IBA FC65-G, and CC13, paired with a PTW UE electrometer) was studied. An in-house built MR-compatible water tank and an accompanying cylindrical insert that allowed chamber rotation around the cylinder's axis was used. The EPID onboard imaging was used to center chamber at the MR-linac isocenter (143.5cm, SAD), as well as to verify position at each datapoint. A clear angular dependence of dose response for all chambers has been measured. The most significant effect of magnetic field on relative chamber response in the presence of magnetic field was observed in the orientation when chamber axis is perpendicular to the direction of magnetic field with the tip pointing in the same direction as Lorentz force. This effect is more pronounced for larger volume chambers; the maximum relative variation in the chamber response (between the setup described above and the one where chamber and magnetic field are parallel) is a 5.3% and 4.6% increase for A19 and FC65-G, respectively, and only 2.0% and 1.9% for smaller volume A1SL and CC13 chamber, respectively. We measured the absolute magnitude of the magnetic field correction factor for the Exradin-A19, A1SL, IBA FC65-G, and CC13 to be 0.938±1.13%, 0.968±0.99%, 0.950±1.13%, and 0.975±1.13%, respectively. The values are for perpendicular orientation of the chamber relative to magnetic field and parallel to the Lorentz force. Experimental measurements carried out in this study have verified the optimal orientation of ionization chamber in terms of minimizing effect of magnetic field on the chamber dose response. This study provides a detailed high-resolution measurement of absolute values for four reference class chambers as a function of the angle between ionization chamber's central axis and the direction of strong magnetic field over a full 360° rotation. The experimental results of this study can further be used for optimization of the actual sensitive volume of the chamber (and analysis of dead volume) in future Monte Carlo chamber simulations in the presence of strong magnetic fields. In addition, it will provide some necessary data for future reference dosimetry protocols for MR-linac.

Interaction of proflavin with tryptophan in reverse micellar microenvironment of AOT: Photoinduced electron transfer probed by magnetic field effect

Photoinduced electron transfer (PET) from a biological amine, tryptophan to a well-known acridine-derivative, proflavin has been investigated employing laser flash photolysis technique in heterogeneous AOT reverse micelles (RMs). In AOT RMs a significant magnetic field effect (MFF) on PET has been observed which authenticates the triplet spin states of the precursors of PET. The measurement of B1⁄2 value gives an indication of the extent of hyperfine interactions present in the system in AOT medium. The cause of discrepancy between calculated and experimental B1⁄2 values is explained. Further, it is observed that MFE decreases with increase in pool size of the RMs which highlights the importance of optimum separation between the corresponding radical ions pairs to maximize MFE.

Magnetic Field Effect on Anodic Dissolution of Axle Steel in Bicarbonate Solution with Chlorides

The vehicle axle in the railway locomotive is a very important component. Localized corrosion is a cause of its degradation. Localized corrosion is usually caused by corrosive environments especially in media containing chloride ions. Harmonic currents in the power supply loops (contact nets and guide rails) of the train during train travel can produce stray current that produces stray magnetic fields. Some studies have shown that magnetic fields can accelerate or inhibit localized corrosion of metals. In this study, optical microscopy (OM) and electrochemical measurements were used to study the effects of magnetic field on the electrochemical behavior and corrosion morphology of axle steel in sodium bicarbonate solutions with and without chloride ions. Different scan rates were used in the measurements of anodic polarization curves. Potentiostatic polarization measurements were performed with applying or removing a 0.4 T magnetic field. The surface morphologies of the electrodes were observed after potentiostatic polarization. Figure 1 show that, for axle steel in 0.05 mol/L NaHCO3 with or without 0.001 mol/L NaCl, the magnetic field increased the peak current, positively shifted the potential for the onset of passivation, and narrowed the passivation range. Chlorides increased the anodic current in the transpassivation region. The synergistic effect of magnetic field and chlorides on breakdown of passivation was more significant at high potential scan rate for the anodic polarization curve measurements. Obvious corrosion pits could be found after polarization, according to the morphology of the axle steel after polarization at a scan rate of 50 mV/min. It is found that the magnetic field significantly accelerated the corrosion. For axle steel in 0.05 mol/L NaHCO3 system, the potentiostatic polarization was carried out at -0.3 V(SCE). The current density decreased with increasing the polarization time. The current decreasing rate was mitigated by applying a 0.4T magnetic field, i.e., the anodic current density tended to be more stable under applied magnetic field, showing a significant magnetic field effect on anodic dissolution and pitting behavior of axle steel in this environments. Figure 1

$\rho^{0} - \omega$ ρ 0 - ω mixing in the presence of a weak magnetic field

We calculate the momentum dependence of the $\rho^0-\omega$ mixing amplitude in vacuum with vector nucleon-nucleon interaction in presence of a constant homogeneous weak magnetic field background. The mixing amplitude is generated by the nucleon-nucleon ($NN$) interaction and thus driven by the neutron-proton mass difference along with a constant magnetic field. We find a significant effect of magnetic field on the mixing amplitude. We also calculate the Charge symmetry violating (CSV) $NN$ potential induced by the magnetic field dependent mixing amplitude. The presence of the magnetic field influences the $NN$ potential substantially which can have important consequences in highly magnetized astrophysical compact objects, such as magnetars. The most important observation of this work is that the mixing amplitude is non-zero, leading to positive contribute to the CSV potential if the proton and neutron masses are taken to be equal.

Temperature dependence of elastic properties in austenite and martensite of Ni-Mn-Ga epitaxial films

Using surface acoustic waves (SAW) the elastic properties of 500 nm thick epitaxial off-stoichiometric Ni-Mn-Ga films prepared by sputtering on MgO substrate were determined in a broad temperature range both in austenite and martensite and across the martensitic transformation. At room temperature the films were in non-modulated martensite with tweed-like microstructure. Structural and magnetic studies proved that the martensitic structure can be considered homogenous on the scale of surface waves owing to the fine twinning. Measured angular dependence of SAW velocities indicated that the averaged in-plane tetragonal structure can be used for the calculation of elastic coefficients in martensite. The phase velocity of SAW showed an anomaly around the phase transition temperature due to changes of the shear elastic coefficients, c'and c44. During cooling there was a gradual softening of c' in austenite. The softening turned to stiffening at the onset of the martensitic transformation while c44 sharply decreased. The shear coefficients for martensite and paramagnetic austenite of the film are comparable to Ni-Mn-Ga bulk single crystal. No significant effect of magnetic field on elastic coefficients was detected in agreement with the bulk.

Magnetic field effects of photocarrier generation in bulk heterojunctions at low temperature.

We report an experimental investigation of the magnetic field effect (MFE) in polymer bulk heterojunction devices at temperatures below 10 K using photocarrier extraction by linearly increasing voltages. The examined devices were composed of an active layer of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester. In the experiments, the delay time (td) dependence of the MFE was investigated in detail. For td < 80 μs, a positive MFE was observed in the field region B < 0.1 T and a negative MFE was observed for B > 0.2 T. For td > 8 ms, only a positive MFE proportional to B2 was observed. For the photocurrent pulse detected immediately after light irradiation, the MFE was negligibly small. In a high magnetic field of 15 T, a significant MFE exceeding 80% was observed at 1.8 K for td = 800 ms. We discuss the results based on a model of triplet-singlet (or singlet-triplet) conversion in the magnetic field and estimate the exchange integral for the charge-transfer exciton in this photovoltaic cell.

SU‐E‐J‐201: Investigation of MRI Guided Proton Therapy

Purpose:Image‐guided radiation therapy has been employed for cancer treatment to improve the tumor localization accuracy. Radiation therapy with proton beams requires more on this accuracy because the proton beam has larger uncertainty and dramatic dose variation along the beam direction. Among all the image modalities, magnetic‐resonance image (MRI) is the best for soft tissue delineation and real time motion monitoring. In this work, we investigated the behavior of the proton beam in magnetic field with Monte Carlo simulations.Methods:A proton Monte Carlo platform, TOPAS, was used for this investigation. Dose calculations were performed with this platform in a 30cmx30cmx30cm water phantom for both pencil and broad proton beams with different energies (120, 150 and 180MeV) in different magnetic fields (0.5T, 1T and 3T). The isodose distributions, dose profiles in lateral and beam direction were evaluated. The shifts of the Bragg peak in different magnetic fields for different proton energies were compared and the magnetic field effects on the characters of the dose distribution were analyzed.Results:Significant effects of magnetic field have been observed on the proton beam dose distributions, especially for magnetic field of 1T and up. The effects are more significant for higher energy proton beam because higher energy protons travel longer distance in the magnetic field. The Bragg peak shift in the lateral direction is about 38mm for 180MeV and 11mm for 120MeV proton beams in 3T magnetic field. The peak positions are retracted back for 6mm and 2mm, respectively. The effect on the beam penumbra and dose falloff at the distal edge of the Bragg peak is negligible.Conclusion:Though significant magnetic effects on dose distribution have been observed for proton beams, MRI guided proton therapy is feasible because the magnetic effects on dose is predictable and can be considered in patient dose calculation.

Effect of Annealing Environment on Low-Temperature Magnetic and Dielectric Properties of EuCo0.5Mn0.5O3

We report the effect of annealing atmosphere on structure and magnetic and dielectric properties of double perovskite-type EuCo0.5Mn0.5O3 (ECMO). Polycrystalline samples prepared by high-temperature reaction were subjected to annealing in different oxygen partial pressures and investigated by powder X-ray diffraction, magnetometry, and ac impedance spectroscopy. While the samples annealed in air or oxygen environment were found to have cation-disordered orthorhombic structure (Pnma), the samples annealed in inert atmosphere have Eu3+ deficient perovskite-type structure. The temperature- and field-dependent magnetizations indicate the ferromagnetic transition around 130 K. The differences in field-cooled and zero-field-cooled magnetization and significant effect of magnetic field on magnetic properties suggest metamagnetic behavior in ECMO. Randomly distributed clusters of ferromagnetically (FM) and antiferromagnetically (AFM) paired magnetic ions and their relative proportions are reflected in their magne...

Inhomogeneity Effect on Solitary Structures in a Magnetized Warm Plasma: Ionization Versus Recombination

In a magnetized inhomogeneous warm plasma having ionization/recombination, usual version of the KdV equation is found to be modified by two additional terms arising due to the inclusion of ionization/recombination and the density gradient in the plasma. The density gradient in the plasma shows its dependence on the ionization/recombination rate, ion-to-electron temperature ratio, obliqueness of the magnetic field and drift velocity of the ions. In the considered plasma, only the compressive solitary structures are found to propagate corresponding to two different types of modes. A significant effect of magnetic field and ion temperature is found on these structures in both the cases of ionization and recombination, though these structures show weak dependence on the charge of the ions. Interestingly the solitons with prominent tailing structures are evolved in the plasma under the effect of stronger density gradient and higher ionization or recombination. The tailing structure with bigger size evolves in the plasma in the case of only recombination, suggesting that the exchange/transfer of energy from the main soliton to its tail is on a greater scale in the case of recombination than the case of ionization. There exists a critical value of the ionization rate at which the tailing structure associated with only the fast (not slow) solitary structure is vanished. Similarly, the tailing structure associated with only the slow (not fast) solitary structure is disappeared at a critical value of recombination rate.

Magic ultramagnetized nuclei in explosive nucleosynthesis

Direct evidence of the presence of 44Ti and content of the isotope in the supernova remnant Cassiopeia A are obtained from the analysis of gamma-ray spectrum of the remnant. A significant excess of observational 44Ti volume on predictions of supernova models can be explained as the magnetization effect in the process of explosive nucleosynthesis. The formation of chemical elements is considered accounting for superstrong magnetic fields predicted for supernovae and neutron stars. Using the arguments of nuclear statistical equilibrium, a significant effect of magnetic field on the nuclear shell energy is demonstrated. The magnetic shift of the most tightly “bound” nuclei from the transition metals of iron series to titanium leads to an exponential increase in the portion of 44Ti and, accordingly to a significant excess of the yield of these products of nucleosynthesis.

Reexamination of magnetic isotope and field effects on adenosine triphosphate production by creatine kinase.

The influence of isotopically enriched magnesium on the creatine kinase catalyzed phosphorylation of adenosine diphosphate is examined in two independent series of experiments where adenosine triphosphate (ATP) concentrations were determined by a luciferase-linked luminescence end-point assay or a real-time spectrophotometric assay. No increase was observed between the rates of ATP production with natural Mg, (24)Mg, and (25)Mg, nor was any significant magnetic field effect observed in magnetic fields from 3 to 1,000 mT. Our results are in conflict with those reported by Buchachenko et al. [J Am Chem Soc 130:12868-12869 (2008)], and they challenge these authors' general claims that a large (two- to threefold) magnetic isotope effect is "universally observable" for ATP-producing enzymes [Her Russ Acad Sci 80:22-28 (2010)] and that "enzymatic phosphorylation is an ion-radical, electron-spin-selective process" [Proc Natl Acad Sci USA 101:10793-10796 (2005)].

Magnetic field effects on the active dissolution of iron

The impact of superimposed magnetic fields on the behavior of iron in 0.05 M H 2SO 4 at low anodic polarization was investigated by means of potentiostatic polarization measurements. Significant magnetic field effects were observed even though the active dissolution reaction in the investigated potential region is formally charge transfer controlled. The current density can be enhanced or reduced dependent on the magnetic field to electrode configuration. The results are discussed in terms of the magnetic field impact on the surface pH value during the anodic dissolution. Our findings are likely to have important consequences for the life-time prediction of ferromagnetic components in electromagnetic devices and for future studies on magneto-electrodeposition processes.

Effects of 60 Hz 14 µT magnetic field on the apoptosis of testicular germ cell in mice

We recently reported that continuous exposure, for 8 weeks, of extremely low frequency (ELF) magnetic field (MF) of 0.1 or 0.5 mT might induce testicular germ cell apoptosis in BALB/c mice. In that report, the ELF MF exposure did not significantly affect the body weight or testicular weight, but significantly increased the incidence of testicular germ cell death. In the present study, we aimed to further characterize the effect of a 16-week continuous exposure to ELF MF of 14 or 200 microT on testicular germ cell apoptosis in mice. There were no significant effects of MF on body weight and testosterone levels in mice. In TUNEL staining (In situ terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick end labeling), germ cells showed a significantly higher apoptotic rate in exposed mice than in sham controls (P < 0.001). TUNEL-positive cells were mainly spermatogonia. In an electron microscopic study, degenerating spermatogonia showed condensation of nuclear chromatin similar to apoptosis. These results indicate that apoptosis may be induced in spermatogenic cells in mice by continuous exposure to 60 Hz MF of 14 microT.

Incommensurate structure of the spin-Peierls compound TiOCl in zero and finite magnetic fields

We report on a detailed single crystal x-ray diffraction study of the unconventional spin-Peierls compound TiOCl. The intermediate phase of TiOCl is characterized by an incommensurate modulation which is virtually identical to that recently found in the homologue compound TiOBr. The first order phase transition between the spin-Peierls ground state and the incommensurate phase reveals the same kind of thermal hysteresis in both its crystal structure and magnetic susceptibility. A weak, but significant magnetic field effect is found for this phase transition with a field induced shift of the transition temperature of $\ensuremath{\Delta}{T}_{c1}=\ensuremath{-}0.13\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for an applied field of $B=10\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ along the chain direction. The field induced changes of the incommensurate crystal structure are compatible with a scenario of competing intrachain and interchain interactions.

Magnetic field effects on cytochrome c-mediated bioelectrocatalytic transformations.

Constant magnetic fields affect many biological transformations, but we lack mechanistic understanding of the processes. The magnetohydrodynamic effect may account for the enhancement of bioelectrocatalytic transformations at interfaces. This is exemplified by the bioelectrocatalyzed cytochrome c-mediated reduction of oxygen and oxidation of lactate in the presence of cytochrome oxidase and lactate dehydrogenase, respectively. We observe significant magnetic field effects on the rates of bioelectrochemical transformations (ca. 3-fold increase) at the functionalized interfaces at field strengths, B, up to 1 T. We show that the limiting current is proportional to the B(1/3)C*(4/3), where C is the concentration of electroactive species. The results may have important implications on the understanding of the magnetic field effects on natural biocatalytic processes at membranes and on the enhancement of biotransformations in biotechnology.

Effects of 50 Hz magnetic field on cell cycle kinetics and the colony forming ability of budding yeast exposed to ultraviolet radiation.

To investigate the effects of extremely low frequency magnetic fields on ultraviolet radiation (UV) exposed budding yeast, haploid yeast (Saccharomyces cerevisiae) cells of the strain SEy2101a were exposed to 50 Hz sine wave magnetic field (MF) of 120 microT with simultaneous exposure to UV radiation. Most of the UV energy was in the UVB range (280-320 nm). The biologically weighted (CIE action spectrum) dose level for the UV radiation was 175 J/m2. We examined whether 50 Hz MF affected the ability of UV irradiated yeast cells to form colonies (Colony Forming Units, CFUs). In addition, the effect of coexposure on cell cycle kinetics was investigated. Although the significant effect of MF on the cell cycle phases of UV exposed yeast cells was seen only at one time point, the overall results showed that MF exposure may influence the cell cycle kinetics at the first cycle after UV irradiation. The effect of our particular MF exposure on the colony forming ability of the UV irradiated yeast cells was statistically significant 420 min after UV irradiation. Moreover, at 240, 360, and 420 min after UV irradiation, there were fewer CFUs in every experiment in (UV+MF) exposed populations than in only UV exposed yeast populations. These results could indicate that MF exposure in conjunction with UV may have some effects on yeast cell survival or growth.

Can an external magnetic field affect the thermal reaction of pentafluorobenzyl chloride with n-butyllithium in hexane?

The magnetic field effects reported in 1973 for the thermal reaction of pentafluorobenzyl chloride with n-butyllithium in hexane were re-examined at 23±3°C with modern techniques. Using a new reaction apparatus, which has an electromagnet (up to 14.9 kG) in a glove box under argon atmosphere (H 2O and O 2<1 ppm), we studied the magnetic field effects on the yields of final products of pentafluorophenylpentane and decafluorodiphenylethane in the absence and presence of an external magnetic field of 14.9 kG. No significant magnetic field effect was observed upon the yields of pentafluorophenylpentane and decafluorodiphenylethane under well-controlled conditions with sufficient repetitions.