Application Of External Magnetic Field Research Articles

A Novel Nanoparticle-Based Method to Isolate DNA From Dried Saliva and Semen Samples

Objectives: Saliva and semen stains may be found at crime scene (suicide, homicide, kidnapping, rape, sexual assault, poisoning, etc.). Through, which DNA can be isolated and individual can be identified. DNA can be of great importance in forensic science investigation to identify individuals. Currently, there are enormous methods to isolate DNA from biological fluids. The current study employed nanoparticle–biomolecule conjugate method to isolate DNA. Materials & Methods: A nanoparticle-biomolecule conjugate is a magnetic nanoparticle with biomolecules attached to its surface. Saliva and semen were collected using cotton swabs from different surfaces (tile, steel, aluminum, glass, iron, wood, etc.) on which saliva and semen were poured and allowed to dry earlier as to create simulated crime scene. Magnetic nanoparticles (Fe3O4) act as solid phase support to isolate DNA from saliva and semen stains. In the current study, cells and spermatozoa were extracted from saliva and semen swabs, respectively. Cell lysis was performed to extract epithelial cells from saliva and spermatozoa from semen and magnetic nanoparticles and biomolecule conjugate were added to the lysed cells to bind to DNA. Results: Application of external magnetic field helped to settle down nanoparticle-biomolecule conjugate and thus separate DNA from other cell components. Spectrophotometer Nanodrop technology was employed to perform the readings, which confirmed the presence of DNA at 260/280 ratio and quality of DNA was compared with the DNA isolated using the two different methods.Conclusion: The current study aimed at developing all new methods to isolate DNA from dried saliva and semen samples using magnetic nanoparticles by reviewing the methods developed earlier to isolate DNA from blood and tissue using magnetic nanoparticles. With modifications in the method and chemical preparation, a new method was successfully developed. DNA was isolated successfully; and confirmation was made by analyzing DNA through Nanodrop spectrophotometer.

Magnetocaloric materials with ultra-small magnetic nanoparticles working at room temperature

Through the use of the Monte Carlo simulations utilising the mean-field approach, we show that a dense assembly of separated ultra-small magnetic nanoparticles embedded into a non-magnetic deformable matrix can be characterized by a large isothermal magnetic entropy change even upon applying a weak magnetic field with values much smaller than one Tesla. We also show that such entropy change may be very significant in the vicinity of the room temperature which effect normally requires an application of a strong external magnetic field. The deformable matrix chosen in this work as a host for magnetic nanoparticles adopts a thin film form with a large surface area to volume ratio. This in turn in combination with a strong magneto-volume coupling exhibited by this material allows us to show its suitability to be used in the case of a variety of applications utilising local cooling/heating such as future magnetic refrigerants.

Design magnetic matrices for cell technology supporting devices

Biomedical applications of magnetic materials are a hot topic of present day research. Special attention is paid for design and development of appropriate instrumentation. In this work magnetic system consisting of an equidistant set of commercial permanent magnets (6 × 4 assay) was proposed, designed and tested for further employment in the experiments in cell cultivation experiments. Magnetic field distribution was experimentally measured in 3 axes: OX, OY, OZ by gaussmeter. The results were statistically analyzed. Constant magnetic field near the center of XY plane was relatively homogeneous but at edges significant value of magnetic field gradient was observed. With increasing of Z distance, the decreasing of magnetic field strength was observed. Obtained parameters of a designed system are satisfactory and therefore it can be recommended for cell cultivation experiments when application of external magnetic field is desired.

Imaging antiferromagnetic domains in nickel oxide thin films by optical birefringence effect

Recent demonstrations of electrical detection and manipulation of antiferromagnets (AFMs) have opened new opportunities towards robust and ultrafast spintronics devices. However, it is difficult to establish the connection between the spin-transport behavior and the microscopic AFM domain states due to the lack of the real-time AFM domain imaging technique under the electric field. Here we report a significant Voigt rotation up to 60 mdeg in thin NiO(001) films at room temperature. Such large Voigt rotation allows us to directly observe AFM domains in thin-film NiO by utilizing a wide-field optical microscope. Further complementary XMLD-PEEM measurement confirms that the Voigt contrast originates from the NiO AFM order. We examine the domain pattern evolution at a wide range of temperature and with the application of external magnetic field. Comparing to large-scale-facility techniques such as the X-ray photoemission electron microscopy, the use with a wide-field, tabletop optical imaging method enables straightforward access to domain configurations of single-layer AFMs.

Analysis of electron and heavy particle velocity distribution under consideration of nonthermal equilibrium arc

AbstractThe circuit breaker is required to interrupt the current in order to prevent the spreading fault current. The reignition caused by the remaining high‐temperature gas in the opening of circuit breaker occurs. As this countermeasure, the external magnetic field application and blast gas to arc are used in order to decrease the arc temperature. It has been reported that the nonthermal equilibrium of arc is remarkable near the electrode and post arc. However, few reports have the analysis of separating electron and heavy particle momentums under consideration of the nonthermal equilibrium because the physical phenomena are complicated in the nonthermal equilibrium. In this paper, the electron and heavy particle velocity distribution under consideration of nonthermal equilibrium arc were analyzed. As a result, it is possible to quantify the electron and heavy particle velocity. The electron velocity distribution is dominant to the electric potential distribution. On the other hand, the heavy particle velocity distribution is dominant to the pressure gradient. Therefore, the difference between the electron and heavy particle velocity distribution was elucidated.

Magnetic-Assisted Cell Alignment within a Magnetic Nanoparticle-Decorated Reduced Graphene Oxide/Collagen 3D Nanocomposite Hydrogel.

Hydrogel scaffolds are particularly interesting for applications in tissue engineering because of their ability to create a favorable environment which mimics in vivo conditions. However, the hierarchically ordered anisotropic structure which is found in many native tissues and cellular components is hard to achieve in 3D scaffolds. In this work, we report the incorporation of magnetic nanoparticle-decorated reduced graphene oxide (m-rGO) within a collagen hydrogel. This magneto-responsive m-rGO aligned within the collagen hydrogel during gelation with the application of a low external magnetic field. This nanocomposite hydrogel with magnetically aligned m-rGO flakes is capable of encapsulating neuroblastoma cells (SH-SY5Y), promoting cell differentiation and inducing oriented cell growth owing to its excellent biocompatibility and electrical conductivity. The directionally oriented and differentiated SH-SY5Y cells within the m-rGO collagen hydrogel showed propagation of calcium signal along the direction of orientation. This method can be applied to creating magnetically responsive materials with potential for various biomedical applications.

P‐11.10: Active Switching of Photonic Nanojet

We exhibit a three‐dimensional (3D) photonic nanojet (PNJ) based on a dielectric microsphere irradiated by a plane wave with the finite‐difference time‐domain (FDTD) method. The influence of surrounding refractive index on PNJ using the FDTD is demonstrated. Furthermore, We propose a switchable PNJ created by a polystyrene (PS) microsphere with nematic liquid crystals (NLCs) surrounded. The orientation of the LC molecules can be controlled by the application of external magnetic field. Our FDTD simulation results show that the PNJ can be switched on and off by modulating the refractive index of the NLCs. The combination of PNJ and NLCs is extremely useful to fabricate integrated optical devices.

Magnetocaloric effect as a signature of quantum level-crossing for a spin-gapped system

Recent research dealing with magnetocaloric effect (MCE) study of antiferromagnetic (AFM) low dimensional spin systems have revealed a number of fascinating ground-state crossover characteristics upon application of external magnetic field. Herein, through MCE investigation we have explored field-induced quantum level-crossing characteristics of one such spin system: (NCP), an AFM spin 1/2 dimer. Experimental magnetization and specific heat data are presented and the data have been employed to evaluate entropy, magnetic energy and magnetocaloric properties. We witness a sign change in magnetic Grüneisen parameter across the level-crossing field BC. An adiabatic cooling is observed at low temperature by tracing the isentropic curves in temperature-magnetic field plane. Energy-level crossover characteristics in NCP interpreted through MCE analysis are well consistent with the observations made from magnetization and specific heat data.

Combination of stearic acid coated magnetic nanoparticle based sonication assisted dispersive solid phase extraction and slotted quartz tube-flame atomic absorption spectrophotometry for the accurate and sensitive determination of lead in red pepper samples and assessment of green profile

This study describes the determination of lead at trace levels by slotted quartz tube flame atomic absorption spectrophotometry (SQT-FAAS) after preconcentration by the help of stearic acid coated magnetic nanoparticle (SAC-MNPs) based sonication assisted dispersive solid phase extraction (SA-DSPE). SAC-MNPs were used due to their easy separation advantages by the application of external magnetic field. All extraction parameters were optimized by response surface methodology based experimental design. The experimented data was evaluated by the analysis of variance. Under the optimum conditions, about 31 folds enhancement in detection power was obtained over the conventional FAAS. The recovery results obtained for samples spiked at 60 and 120 ng mL−1 were 106.6 and 102.6%, respectively, validating the method as accurate and applicable to the red pepper matrix. The percent relative standard deviations of the results were under 5.0% even at low concentrations that established high precision for replicate extractions and instrumental readings.

Room temperature ferrimagnetism in Yb-doped relaxor ferroelectric PbFe2/3W1/3O3

We report ferrimagnetism and reentrant relaxor ferroelectricity near room temperature in a Yb-doped PbFe2/3W1/3O3 cubic perovskite. Structural analysis reveals the presence of a single cubic perovskite phase, with the Fm3¯m space group [lattice parameter: a = 8.0112(3) Å], and partial B-site ordering. The B-site ordering yields uncompensated magnetic moments in the antiferromagnetic structure of PbFe2/3W1/3O3 and ferrimagnetism near room temperature. An excess moment of ∼0.6 μB/B-site may be estimated from magnetic hysteresis curves recorded up to 50 kOe at 5 K. The temperature dependent magnetodielectric study reveals a sequential phase transition from a long-range ferroelectric state (across 280 K) to a short-range relaxor ferroelectric state (across 190 K). The long-range ferroelectric ordering is found to be more affected by the application of external magnetic fields than the relaxor phase.

A physical model for the characterization of magnetic hydrogels subject to external magnetic fields

Abstract Magnetic hydrogels are interesting nanomaterials able to change their shape and temperature if exposed to external magnetic fields. Thanks to these features, which originate from the microstructure of magnetic hydrogels (magnetic nanoparticles tied together through polymeric chains), these substances have several applications in technological fields and biomedicine. Hydrogels are able to absorb and release large amounts of water, which makes them eligible materials for drug delivery. This feature is made even more attractive in cases where the delivery/release can be externally controlled. Controlling the system using external magnetic fields requires keystone processes like modeling and simulation. In this paper, the properties of the system have been analyzed using a 2D microscopical simulation of a suitable physical model. Experimentally, the behavior of the system with and without the application of external magnetic fields and its dissipative effects have been characterized. Specifically, we analyze the change of size and temperature of an hydrogel system as a function of the external magnetic field frequency, thus providing a fundamental tool for developing magnetic substances suitable for specific applications.

Observation of Coherent Population Trapping in Ensembles of Diamond NV-Centers under Ground-State Level Anticrossing Conditions

The coherent population trapping effect in ensembles of diamond NV-centers under ground-state level anticrossing conditions was implemented with the application of a strong external magnetic field oriented along the [111] crystal axis.

Magnetoplasmonic isolators based on graphene waveguide ring resonators

Nanoscale optical isolators are crucial for nanophotonic, quantum-optical, and optoelectronic applications and have attracted considerable attention recently. The application of external magnetic fields is the standard way for creating nonreciprocity as the basis for optical isolation. However, the magneto-optical response is usually small, thus it should be enhanced to create strong enough nonreciprocity for high-contrast isolation. We demonstrate that a graphene waveguide ring resonator allows a nanoscale platform for a high-contrast optical isolator. Graphene provides strong subwavelength confinement and low loss, therefore large nonreciprocity can be realized for ultracompact high-contrast isolators by plasmon resonance enhancement combined with resonator resonance enhancement. The resonance frequency is widely tunable by controlling the gate voltages of the rolling graphene sheet of a graphene resonator. Manipulation of the waveguide-resonator coupling can be achieved by controlling the gate voltage of the planar graphene sheet. The concept of magnetically biased ultracompact graphene waveguide ring resonators for one-way plasmon flow allows one to tune the operation band over a one-octave-spanning broad frequency range, keeping the contrast higher than 99% and a moderate insertion loss lower than 50%. High performance is achievable by only adjusting both gate voltages of the planar and rolling graphene sheets.

Magnetic-Competition-Induced Colossal Magnetoresistance in n -Type HgCr2Se4 under High Pressure

The n-type HgCr_{2}Se_{4} exhibits a sharp semiconductor-to-metal transition (SMT) in resistivity accompanying the ferromagnetic order at T_{C}=106 K. Here, we investigate the effects of pressure and magnetic field on the concomitant SMT and ferromagnetic order by measuring resistivity, dc and ac magnetic susceptibility, as well as single-crystal neutron diffraction under various pressures up to 8GPa and magnetic fields up to 8T. Our results demonstrate that the ferromagnetic metallic ground state of n-type HgCr_{2}Se_{4} is destabilized and gradually replaced by an antiferromagnetic, most likely a spiral magnetic, and insulating ground state upon the application of high pressure. On the other hand, the application of external magnetic fields can restore the ferromagnetic metallic state again at high pressures, resulting in a colossal magnetoresistance (CMR) as high as ∼ 3×10^{11}% under 5T and 2K at 4GPa. The present study demonstrates that n-type HgCr_{2}Se_{4} is located at a peculiar critical point where the balance of competition between ferromagnetic and antiferromagnetic interactions can be easily tipped by external stimuli, providing a new platform for achieving CMR in a single-valent system.

Spin dynamics of hot excitons in diluted magnetic semiconductors with spin-orbit interaction

We explore the impact of a Rashba-type spin-orbit interaction in the conduction band on the spin dynamics of hot excitons in diluted magnetic semiconductor quantum wells. In materials with strong spin-orbit coupling, we identify parameter regimes where spin-orbit effects greatly accelerate the spin decay and even change the dynamics qualitatively in the form of damped oscillations. Furthermore, we show that the application of a small external magnetic field can be used to either mitigate the influence of spin-orbit coupling or entirely remove its effects for fields above a material-dependent threshold.

Quantum Spin Hall Materials

AbstractThe quantum spin Hall (QSH) effect describes the state of matter in certain 2D electron systems, in which an insulating bulk state arises together with helical states at the edge of the sample. In stark contrast to its closest kin, the integer quantum Hall state, the QSH state exists only in time‐reversal symmetric system (e.g., in non‐magnetic materials and without the application of external magnetic field). This article reviews the development of the understanding and construction of the QSH states after their first theoretical proposal, with an emphasis on the materials perspective. Certain semiconductor quantum wells and 2D materials with strong spin–orbit coupling have been found to support QSH states.

Magneto-visco-hyperelasticity for hard-magnetic soft materials: theory and numerical applications

Soft materials that can deform under external stimuli offer great opportunities for the development of new structural applications such as sensor-actuator systems, soft robots or biomedical devices. Among these materials, soft polymers filled with magnetic particles are experiencing an increasing interest from the scientific community. Apart from magnetorheological elastomers and ferrogels, a new magneto-sensitive material type has been developed recently. These so-called hard-magnetic materials allow for shape-programmability by the addition of magnetically-hard particles within a polymeric matrix. In this regard, constitutive and computational frameworks describing the magneto-mechanics of such materials are needed to provide new avenues in the development of novel applications based on hard-magnetic soft polymers. To this end, this work focuses on the mathematical modelling of the magneto-mechanics of hard-magnetic soft materials and their implementation in finite element (FE) frameworks. The proposed continuum model is formulated for large deformations and within a thermodynamically consistent framework. In addition, the model incorporates viscous contributions to account for relaxation and dissipation effects in the deformation process of these materials when subjected to external magnetic fields and/or mechanical loading. To illustrate the theory, the magneto-mechanical model is implemented within an implicit static FE framework and three numerical examples are provided to explore potential applications as well as to evaluate the influence of the external magnetic field application on the viscoelastic response of the material. Finally, the framework is implemented in an implicit dynamic FE framework to evaluate the role of inertial terms on the dynamic response of these materials.

Investigation of giant dielectric and room temperature ferromagnetic response of facile CZTO nanostructure

Cubic CoZnTiO4 (CZTO) nanocomposite structure has been synthesized via a modest chemical method at a much lower calcination temperature. The possible phase formations and crystalline nature of the as synthesized structure has been studied by X-ray diffraction technique. FESEM micrographs depict the grain growth within the nanocomposite. Thermal analysis shows endothermic as well as exothermic peaks which points out the thermal stability over the observed temperature range. The synthesized CZTO nanocomposite structure shows nearly frequency independent giant dielectric response on application of external electric field. The nanostructure shows e′ ~ 21,000 at 40 Hz frequency. With the help of internal barrier layer capacitor model, the origin of this large dielectric constant is well explained. The impedance spectroscopy analysis and equivalent circuit response also supports the obtained result. On application of external magnetic field, the synthesized CZTO sample also shows room temperature ferromagnetic response. This magneto-dielectric response of CZTO nanostructure enables it to be a superior material for forthcoming device application.

Energy Storage: Giant Enhancement in the Supercapacitance of NiFe–Graphene Nanocomposites Induced by a Magnetic Field (Adv. Mater. 28/2019)

The application of external magnetic fields to NiFe–graphene nanocomposites during the galvanostatic charge/discharge cycles induces a dramatic metal phase segregation, forming nanometric metal clusters of Ni with an outstanding electrochemical activity. This metal segregation leads to an enhancement in the capacitance of the nanocomposite, as described by Gonzalo Abellán, Eugenio Coronado, and co-workers in article number 1900189.

Variations of the Static Contact Angle of Ferrofluid Droplets on Solid Horizontal Surfaces in External Uniform Magnetic Fields.

The application of external uniform magnetic fields to ferrofluid droplets affects their magnetic order at the nanoscale as well as their shape at the macroscale, thus changing their contact angle with the surface. In this work, the effects of external uniform magnetic fields on the contact angles between different oil-based ferrofluid droplets and a handful of horizontal surfaces of varying wettability were studied. The contact angle is no longer constant around the ferrofluid droplet; rather, it varies in a rich yet predictable way. Droplets dispensed in the presence of the magnetic field on oleophobic surfaces adjust such that the contact angle increases at the front and back ends and decreases at the two perpendicular positions. The opposite behavior is reported for ferrofluid droplets on oleophilic surfaces. These direction-dependent changes in the contact angle can have a significant impact on the behavior of ferrofluid droplets on gradient surfaces where they can either diminish or enhance the surface tension gradient. Our work is fundamentally relevant to potential applications involving the controlled movement of ferrofluid droplets on surfaces like the lab-on-a-chip under the combined effects of a magnetic field and either a surface tension gradient or an electric field (i.e., electrowetting). It is important to understand how the two effects interact for the optimal utilization of these effects in future applications.