In-tissue embedded magnetic nanoparticle (MNPs) detection is one of the most interesting cases for cancer research. In order to understand the origin, the limits and the way of improvement of ...magnetic biosensor sensitivity for the detection of 3D mezoscopic distributions of MNPs, we have developed a magnetoimpedance biosensor prototype with a Cu (3 nm)/FeNi(100 nm)5/Cu(500 nm)/FeNi(100 nm)/Cu(3 nm)5 rectangular sensitive element. Magnetoimpedance (MI) responses were measured with and without polyacrylamide ferrogel layer mimicking natural tissue in order to evaluate stray fields of embedded MNPs of γ-Fe2O3 iron oxide. A model for MI response based on a solution of Maxwell equations with Landau-Lifshitz equation was developed in order to understand the origin of the prototype sensitivity which reached 1.3% of ΔZ/Z per 1% of MNPs concentration by weight. To make this promising technique useful for magnetically labeled tissue detection, a synthesis of composite gels with MNPs agglomerates compactly located inside pure gel and their MI testing are still necessary.
•Magnetoimpedance (MI) biosensor prototype with Cu/FeNi5/Cu/FeNi/Cu5 element was designed and tested.•MI responses were measured with and without ferrogel layer mimicking natural tissue.•We were able to evaluate stray fields of 3D distributions of embedded magnetic nanoparticles.•Electromagnetic MI model was developed in order to understand the 1.3% of ΔZ/Z per 1 wt% of MNPs concentration prototype sensitivity.
Thermal activation of transient receptor potential (TRP) cation channels is one of the most striking examples of temperature-controlled processes in cell biology. As the evidence indicating the ...fundamental role of such processes in thermosensation builds at a fast pace, adequately accurate tools that would allow heat receptor logic behind thermosensation to be examined on a single-cell level are in great demand. Here, we demonstrate a specifically designed fiber-optic probe that enables thermal activation with simultaneous online thermometry of individual cells expressing genetically encoded TRP channels. This probe integrates a fiber-optic tract for the delivery of laser light with a two-wire microwave transmission line. A diamond microcrystal fixed on the fiber tip is heated by laser radiation transmitted through the fiber, providing a local heating of a cell culture, enabling a well-controlled TRP-assisted thermal activation of cells. Online local temperature measurements are performed by using the temperature-dependent frequency shift of optically detected magnetic resonance, induced by coupling the microwave field, delivered by the microwave transmission line, to nitrogen--vacancy centers in the diamond microcrystal. Activation of TRP channels is verified by using genetically encoded fluorescence indicators, visualizing an increase in the calcium flow through activated TRP channels.
•Enthalpies of solution of hybrid perovskites CH3NH3PbX3 (X=Cl, Br, I) in DMSO were measured using solution calorimetry.•Standard enthalpies and Gibbs free energies of formation of CH3NH3PbX3 (X=Cl, ...Br, I) from halides were calculated on the basis of experimental data.•Entropy contribution was shown to play a major role in the stability of hybrid organic–inorganic perovskites.
Enthalpies of solution of hybrid perovskites CH3NH3PbX3 (X=Cl, Br, I) in DMSO were measured using solution calorimetry. Standard enthalpies and Gibbs free energies of formation of CH3NH3PbX3 (X=Cl, Br, I) hybrid perovskites from halides as well as from elements at 298K were calculated on the basis of experimental data obtained and compared with the data available in literature. Excellent agreement was obtained between the standard Gibbs free energy of decomposition of CH3NH3PbX3 into solid PbX2, gaseous HX and methylamine calculated on the basis of our data and that evaluated on the basis of vapor pressure measurement results reported by other authors. Entropy contribution was shown to play a major role in the stability of hybrid organic–inorganic perovskites with respect to their decomposition on constituent halides.
Magnetic biosensors are an important part of biomedical applications of magnetic materials. As the living tissue is basically a "soft matter." this study addresses the development of ferrogels (FG) ...with micron sized magnetic particles of magnetite and strontium hexaferrite mimicking the living tissue. The basic composition of the FG comprised the polymeric network of polyacrylamide, synthesized by free radical polymerization of monomeric acrylamide (AAm) in water solution at three levels of concentration (1.1 M, 0.85 M and 0.58 M) to provide the FG with varying elasticity. To improve FG biocompatibility and to prevent the precipitation of the particles, polysaccharide thickeners-guar gum or xanthan gum were used. The content of magnetic particles in FG varied up to 5.2 wt % depending on the FG composition. The mechanical properties of FG and their deformation in a uniform magnetic field were comparatively analyzed. FG filled with strontium hexaferrite particles have larger Young's modulus value than FG filled with magnetite particles, most likely due to the specific features of the adhesion of the network's polymeric subchains on the surface of the particles. FG networks with xanthan are stronger and have higher modulus than the FG with guar. FG based on magnetite, contract in a magnetic field 0.42 T, whereas some FG based on strontium hexaferrite swell. Weak FG with the lowest concentration of AAm shows a much stronger response to a field, as the concentration of AAm governs the Young's modulus of ferrogel. A small magnetic field magnetoimpedance sensor prototype with Co
Fe
Mo
Si
B
rapidly quenched amorphous ribbon based element was designed aiming to develop a sensor working with a disposable stripe sensitive element. The proposed protocol allowed measurements of the concentration dependence of magnetic particles in gels using magnetoimpedance responses in the presence of magnetite and strontium hexaferrite ferrogels with xanthan. We have discussed the importance of magnetic history for the detection process and demonstrated the importance of remnant magnetization in the case of the gels with large magnetic particles.
The axon initial segment is a specialized compartment of the proximal axon of CNS neurons where action potentials are initiated. However, it remains unknown whether this domain is assembled in ...sensory dorsal root ganglion neurons, in which spikes are initiated in the peripheral terminals. Here we investigate whether sensory neurons have an axon initial segment and if it contributes to spontaneous activity in neuropathic pain. Our results demonstrate that myelinated dorsal root ganglion neurons assemble an axon initial segment in the proximal region of their stem axon, enriched in the voltage-gated sodium channels Nav1.1 and Nav1.7. Using correlative immunofluorescence and calcium imaging, we demonstrate that the Nav1.7 channels at the axon initial segment are associated with spontaneous activity. Computer simulations further indicate that the axon initial segment plays a key role in the initiation of spontaneous discharges by lowering their voltage threshold. Finally, using a Cre-based mouse model for time-controlled axon initial segment disassembly, we demonstrate that this compartment is a major source of spontaneous discharges causing mechanical allodynia in neuropathic pain. Thus, an axon initial segment domain is present in sensory neurons and facilitates their spontaneous activity. This study provides a new insight in the cellular mechanisms that cause pathological pain and identifies a new potential target for chronic pain management.
When using a second-order Schrödinger-type equation with the effective potential of the Schwarzschild field, the existence of a stationary state of half-spin particles with energy
E
= 0 is proved. ...For each of the values of quantum numbers
j
,
l
, the physically meaningful energy
E
= 0 (the binding energy is
) is implemented at the value of the gravitational coupling constant
. The particles with
E
= 0 are, with the overwhelming probability, at some distance from the event horizon within the range from zero to several fractions of the Compton wavelength of a fermion depending on value of the gravitational coupling constants and the values of
j
,
l
. In this paper, similar solutions of the second-order equation are announced for bound states of fermions in the Reissner–Nordström, Kerr, Kerr–Newman fields. Atomic-type systems (the point sources of the Schwarzschild gravitational field) with fermions in bound states are proposed as particles of dark matter.
•We have prepared a new nanomaterial Fe48Ni52 by the EEW technique.•X-ray diffraction, BET, magnetization and microwave absorption were studied.•The electron microscopies showed that the grains are ...spherical in shape.•The field variation of the microwave loss required a deeper structural investigation.•HRTEM revealed the presence of “twinned” layers inside the grains.
Magnetic nanoparticles (MNPs) of FeNi were prepared by the electric explosion of wire aiming to obtain a large batch of magnetic nanomaterial with enhanced effective magnetization. X-ray diffraction, transmission, scanning electron microscopy, low temperature nitrogen adsorption, magnetization and microwave absorption measurements were used for full characterization. The shape of the MNPs with weight averaged mean diameter of 69±8nm, was very close to being spherical. The saturation magnetization of about 140emu/g up for 300K was established. The room temperature microwave signal was very complex due to sizable zero field absorption and various contributions. We obtain reasonable agreement between structural magnetic and microwave techniques by taking into account the presence of so-called “twin” structure in the MNPs.
Magnetic metallic nanoparticles (MNPs) of Ni, Ni82Fe18, Ni50Fe50, Ni64Fe36, and Fe were prepared by the technique of the electrical explosion of metal wire. The average size of the MNPs of all types ...was in the interval of 50 to 100 nm. Magnetic polymeric composites based on polyvinyl butyral with embedded metal MNPs were synthesized and their structural, adhesive, and magnetic properties were comparatively analyzed. The interaction of polyvinyl butyral (supplied as commercial GE cryogenic varnish) with metal MNPs was studied by microcalorimetry. The enthalpy of adhesion was also evaluated. The positive values of the enthalpy of interaction with GE increase in the series Ni82Fe18, Ni64Fe36, Ni50Fe50, and Fe. Interaction of Ni MNPs with GE polymer showed the negative change in the enthalpy. No interfacial adhesion of GE polymer to the surface of Fe and permalloy MNPs in composites was observed. The enthalpy of interaction with GE polymer was close to zero for Ni95Fe5 composite. Structural characterization of the GE/Ni composites with the MNPs with the lowest saturation magnetization confirmed that they tended to be aggregated even for the materials with lowest MNPs concentrations due to magnetic interaction between permalloy MNPs. In the case of GE composites with Ni MNPs, a favorable adhesion of GE polymer to the surface of MNPs was observed.
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