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1.
J Colloid Interface Sci ; 606(Pt 2): 1918-1927, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34695759

RESUMO

Developing metal-organic frameworks (MOFs) derived microwave absorbers with the merits of thin matching thickness, broad bandwidth and strong absorption still remains a big challenge in the electromagnetic absorption field. Herein, FeNi-MOFs derived magnetic-carbon composites were fabricated via a solvothermal and pyrolytic two-step strategy. It was found that the micromorphology of carbon frameworks could be regulated from the regular octahedron to spherical shape through facilely adjusting the molar ratios of Fe3+ to Ni2+ in the precursors. Furthermore, results revealed that the molar ratios of Fe3+ to Ni2+ had notable effects on the electromagnetic parameters and microwave attenuation capacity of attained composites. Significantly, the obtained FeNi/C composite with the molar ratio of Fe3+ to Ni2+ of 1:0.5 showed the comprehensively optimal electromagnetic attenuation performance, i.e. the reflection loss achieved -40.2 dB (larger than 99.99% absorption) and absorption frequency band was as high as 5.8 GHz (from 11.9 to 17.7 GHz, covering 96.7% of Ku-band) under an ultrathin thickness of 1.65 mm. Besides, the probable microwave dissipation mechanisms were clarified, which mainly derived from the optimized impedance matching, strengthened interfacial polarization and dipole polarization relaxation, enhanced conduction loss and natural resonance effect. Therefore, our results would be helpful for designing and developing high-performance microwave absorbing composites derived from MOFs.


Assuntos
Estruturas Metalorgânicas , Micro-Ondas , Carbono , Magnetismo , Pirólise
2.
Sci Total Environ ; 804: 150293, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34798762

RESUMO

Molecularly imprinted polymers (MIPs) have added a vital contribution to food quality and safety with the effective extraction of pesticide residues due to their unique properties. Magnetic molecularly imprinted polymers (MMIPs) are a superior approach to overcome stereotypical limitations due to their unique core-shell and novel composite structure, including high chemothermal stability, rapid extraction, and high selectivity. Over the past two decades, different MMIPs have been developed for pesticide extraction in actual food samples with a complex matrix. Nevertheless, such developments are desirable, yet the synthesis and mode of application of MMIP have great potential as a green chemistry approach that can significantly reduce environmental pollution and minimize resource utilization. In this review, the MMIP application for single or multipesticide detection has been summarized by critiquing each method's uniqueness and efficiency in real sample analysis and providing a possible green chemistry exploration procedure for MMIP synthesis and application for escalated food and environmental safety.


Assuntos
Impressão Molecular , Resíduos de Praguicidas , Fenômenos Magnéticos , Magnetismo , Polímeros Molecularmente Impressos , Resíduos de Praguicidas/análise , Extração em Fase Sólida
3.
J Colloid Interface Sci ; 605: 425-431, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34332415

RESUMO

Latent fingerprint recognition technique has received increasing attention because it helps to precisely identify human information for many applications. In this study, bifunctional core-shell magnetic fluorescent microspheres have been synthesized via a facile interface Pechini-type sol-gel method using citric acid and polyethylene glycol as chelating agent and cross-linking agent, respectively. The obtained Fe3O4@YVO4:Eu3+ microspheres possess a typical core-shell structure, large magnetization, and strong fluorescence emission. The surface morphology and roughness of the microspheres can be flexibly tuned by controlling the multistep interface deposition process and subsequent calcination temperatures. Due to their well-integrated bifunctionalities, these magnetic fluorescent microspheres show outstanding performance in the visualization of latent fingerprints on various substrates with high definition and excellent anti-interference, and therefore they have great potential for application in identity recognition.


Assuntos
Magnetismo , Dióxido de Silício , Humanos , Fenômenos Magnéticos , Microesferas
4.
J Nanosci Nanotechnol ; 21(6): 3178-3182, 2021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-34739773

RESUMO

The magnetic α-Fe2O3/Fe3O4 heterostructure nanorods were fabricated by an alcohol-solution direct combustion method. The influence of the calcination temperature on the composition and properties of the nanorods was investigated. When the calcination temperature was not greater than 400 °C, the magnetic α-Fe2O3/Fe3O4 heterostructure nanorods were obtained, and the saturation magnetization (Ms) of the magnetic α-Fe2O3/Fe3O4 heterostructure nanorods decreased with the calcination temperature increasing from 250 °C to 400 °C; when the calcination temperature was equal or greater than 450 °C, α-Fe2O3 nanorods were obtained. In addition, the effects of nanorods' concentration, nanorods' constituent, incubation time and magnetic field on A549 cytotoxicity were investigated. The cytotoxicity of the heterostructure nanorods appeared time-dependent and concentration-dependent, and the magnetic field could enhance the cytotoxicity of nanorods to A549.


Assuntos
Compostos Férricos , Nanotubos , Células A549 , Compostos Férricos/toxicidade , Humanos , Fenômenos Magnéticos , Magnetismo , Nanotubos/toxicidade
5.
J Nanosci Nanotechnol ; 21(6): 3588-3595, 2021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-34739811

RESUMO

In this work, the capturing of magnetic nanoparticles has been explored through a mathematical model and in-vitro study in a cylindrical tube under the influence of an applied magnetic field. In the formulation of the model, the dominant magnetization and drag forces are included that extensively affect the capturing of magnetic nanoparticles. Model results indicates that the value of capture efficiency (CE) improves 23 to 51% for the magnetic field 0.1 to 0.5 T, respectively. It is further noticed through in-vitro experimental results that capturing of magnetic particles increases by the external magnetic field, applied through an electromagnet at the centre of the cylindrical tube. The experimental value of capture efficiency is calculated via the analysis of the captured images of the particles and Atomic Absorption Spectroscopy (AAS) data. The in-vitro experimental and model results are compared, which demonstrates good agreement and consequently validates the mathematical model.


Assuntos
Nanopartículas de Magnetita , Nanopartículas , Sistemas de Liberação de Medicamentos , Campos Magnéticos , Magnetismo
6.
Anal Chim Acta ; 1186: 339099, 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34756265

RESUMO

Functional materials with good biocompatibility have been widely used in the study of genomics, proteomics and disease diagnosis, which has improved the progress of life science. In this paper, the material not only exhibited a strong affinity to the phosphate groups on the exosomal membrane due to the coexistence of Zr-O clusters and Ti4+, but also owned great hydrophilicity to reduce non-specific adsorption of contaminated proteins, achieving the separation and purification of exosomes from complex biosamples. The model exosomes extracted by ultracentrifugation (UC) were used to evaluate the feasibility of Fe3O4@UiO-66-NH2@PA-Ti4+ capturing exosomes. The process of Fe3O4@UiO-66-NH2@PA-Ti4+ capturing exosomes was simple to operate with a high recovery rate (97.3%) within a short time (5 min). Then Fe3O4@UiO-66-NH2@PA-Ti4+ was further applied to capture exosomes in media and urine followed by the downstream proteomics analysis. 348 and 284 exosomal proteins were identified for cell medium and urine, respectively. This work shows great potential of the material for subsequent function research of disease-related exosomes by separating exosomes rapidly and efficiently.


Assuntos
Exossomos , Nanopartículas de Magnetita , Estruturas Metalorgânicas , Interações Hidrofóbicas e Hidrofílicas , Magnetismo
7.
Sensors (Basel) ; 21(21)2021 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-34770373

RESUMO

The use of magnetic nanoparticles (MNPs) in biomedical applications requires the quantitative knowledge of their quantitative distribution within the body. AC Biosusceptometry (ACB) is a biomagnetic technique recently employed to detect MNPs in vivo by measuring the MNPs response when exposed to an alternate magnetic field. The ACB technique presents some interesting characteristics: non-invasiveness, low operational cost, high portability, and no need for magnetic shielding. ACB conventional methods until now provided only qualitative information about the MNPs' mapping in small animals. We present a theoretical model and experimentally demonstrate the feasibility of ACB reconstructing 2D quantitative images of MNPs' distributions. We employed an ACB single-channel scanning approach, measuring at 361 sensor positions, to reconstruct MNPs' spatial distributions. For this, we established a discrete forward problem and solved the ACB system's inverse problem. Thus, we were able to determine the positions and quantities of MNPs in a field of view of 5×5×1 cm3 with good precision and accuracy. The results show the ACB system's capabilities to reconstruct the quantitative spatial distribution of MNPs with a spatial resolution better than 1 cm, and a sensitivity of 1.17 mg of MNPs fixed in gypsum. These results show the system's potential for biomedical application of MNPs in several studies, for example, electrochemical-functionalized MNPs for cancer cell targeting, quantitative sensing, and possibly in vivo imaging.


Assuntos
Nanopartículas de Magnetita , Animais , Diagnóstico por Imagem , Campos Magnéticos , Magnetismo , Cintilografia
8.
Sensors (Basel) ; 21(22)2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34833661

RESUMO

By using the stress-impedance (SI) effect of a soft magnetic amorphous FeCuNbSiB alloy, a micromachined force sensor was fabricated and characterized. The alloy was used as a sputtered thin film of 500 nm thickness. To clarify the SI effect in the used material as a thin film, its magnetic and mechanical properties were first investigated. The stress dependence of the magnetic permeability was shown to be caused by the used transducer effect. The sputtered thin film also exhibited a large yield strength of 983 GPa. Even though the fabrication technology for the device is very simple, characterization revealed a gauge factor (GF) of 756, which is several times larger than that achieved with conventional transducer effects, such as the piezoresistive effect. The fabricated device shows great application potential as a tactile sensor.


Assuntos
Magnetismo , Tato , Impedância Elétrica
9.
Sensors (Basel) ; 21(22)2021 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-34833789

RESUMO

The Overhauser magnetometer is a scalar quantum magnetometer based on the dynamic nuclear polarization (DNP) effect in the Earth's magnetic field. Sensitivity is a key technical specification reflecting the ability of instruments to sense small variations of the Earth's magnetic field and is closely related to the signal-to-noise ratio (SNR) of the free induction decay (FID) signal. In this study, deuterated 15N TEMPONE radical is used in our sensor to obtain high DNP enhancement. The measured SNR of the FID signal is approximately 63/1, and the transverse relaxation time T2 is 2.68 s. The direct measurement method with a single instrument and the synchronous measurement method with two instruments are discussed for sensitivity estimation in time and frequency domains under different electromagnetic interference (EMI) environments and different time periods. For the first time, the correlation coefficient of the magnetic field measured by the two instruments is used to judge the degree of the influence of the environmental noise on the sensitivity estimation. The sensitivity evaluation in the field environment is successfully realized without electrical and magnetic shields. The direct measurement method is susceptible to EMI and cannot work in general electromagnetic environments, except it is sufficiently quiet. The synchronous measurement method has an excellent ability to remove most natural and artificial EMIs and can be used under noisy environments. Direct and synchronous experimental results show that the estimated sensitivity of the JOM-4S magnetometer is approximately 0.01 nT in time domain and approximately 0.01 nT/Hz in frequency domain at a 3 s cycling time. This study provides a low-cost, simple, and effective sensitivity estimation method, which is especially suitable for developers and users to estimate the performance of the instrument.


Assuntos
Campos Magnéticos , Magnetismo , Eletricidade , Razão Sinal-Ruído
10.
Sensors (Basel) ; 21(22)2021 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-34833802

RESUMO

Magnetic induction tomography (MIT) is a contactless, low-energy method used to visualize the conductivity distribution inside a body under examination. A particularly demanding task is the three-dimensional (3D) imaging of voluminous bodies in the biomedical impedance regime. While successful MIT simulations have been reported for this regime, practical demonstration over the entire depth of weakly conductive bodies is technically difficult and has not yet been reported, particularly in terms of more realistic requirements. Poor sensitivity in the central regions critically affects the measurements. However, a recently simulated MIT scanner with a sinusoidal excitation field topology promises improved sensitivity (>20 dB) from the interior. On this basis, a large and fast 3D MIT scanner was practically realized in this study. Close agreement between theoretical forward calculations and experimental measurements underline the technical performance of the sensor system, and the previously only simulated progress is hereby confirmed. This allows 3D reconstructions from practical measurements to be presented over the entire depth of a voluminous body phantom with tissue-like conductivity and dimensions similar to a human torso. This feasibility demonstration takes MIT a step further toward the quick 3D mapping of a low conductive and voluminous object, for example, for rapid, harmless and contactless thorax or lung diagnostics.


Assuntos
Magnetismo , Tomografia , Condutividade Elétrica , Impedância Elétrica , Humanos , Imageamento Tridimensional , Imagens de Fantasmas
11.
Sheng Wu Gong Cheng Xue Bao ; 37(9): 3190-3200, 2021 Sep 25.
Artigo em Chinês | MEDLINE | ID: mdl-34622627

RESUMO

The targeting of anti-tumor drugs is an important means of tumor treatment and reducing drug side effects. Oxygen-depleted hypoxic regions in the tumour, which oxygen consumption by rapidly proliferative tumour cells, are generally resistant to therapies. Magnetotactic bacteria (MTB) are disparate array of microorganism united by the ability to biomineralize membrane-encased, single-magnetic-domain magnetic crystals (magnetosomes) of minerals magnetite or greigite. MTB by means of flagella, migrate along geomagnetic field lines and towards low oxygen concentrations. MTB have advantage of non-cytotoxicity and excellent biocompatibility, moreover magnetosomes (BMs) is more powerful than artificial magnetic nanoparticles(MNPs). This review has generally described the biological and physical properties of MTB and magnetosomes, More work deals with MTB which can be used to transport drug into tumor based on aerotactic sensing system as well as the competition of iron which is a key factor to proliferation of tumor. In addition, we summarized the research of magnetosomes, which be used as natural nanocarriers for chemotherapeutics, antibodies, vaccine DNA. Finally, We analyzed the problems faced in the tumor treatment using of MTB and bacterial magnetosomes and prospect development trends of this kind of therapy.


Assuntos
Magnetossomos , Neoplasias , Bactérias , Óxido Ferroso-Férrico , Bactérias Gram-Negativas , Magnetismo , Neoplasias/terapia
12.
Anal Chim Acta ; 1184: 339054, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34625272

RESUMO

Immobilized antibodies with site-specific, oriented, and covalent pattern are of great significance to improve the sensitivity of solid-phase immunoassay. Here, we developed a novel antibody conjugation strategy that can immobilize antibodies in a directional and covalent manner. In this study, an IgG-Fc binding protein (Z domain) carrying a site-specific photo-crosslinker, p-benzoyl-L-phenylalanine, and a single C-terminal cysteine (Cys) handle was genetically engineered. Upon UV irradiation, the chimeric protein enables the Cys handle to couple with the native antibody in Fc-specific and covalent conjugation pattern, resulting in a novel thiolated antibody. Thus, an approach for the covalent, directional immobilization of antibodies to maleimide-modified magnetic nanoparticles (MNPs) was developed on the basis of the crosslinking between sulfhydryl and maleimide groups. The antibody-conjugated MNPs were applied in MNP-based enzyme-linked immunosorbent assay (ELISA) for the detection of carcinoembryonic antigen. The MNP-based ELISA presented a quantification linear range of 0.1-100 ng mL-1 and detection limit of 0.02 ng mL-1, which was approximately 100 times more sensitive than the traditional microplate ELISA (2.0 ng mL-1). Thus, the proposed antibody immobilization approach can be used in surface functionalization for the sensitive detection of various biomarkers.


Assuntos
Proteínas de Transporte , Nanopartículas de Magnetita , Anticorpos , Antígenos , Magnetismo
13.
Sensors (Basel) ; 21(20)2021 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-34695941

RESUMO

Soft magnetic materials are widely requested in electronic and biomedical applications. Co-based amorphous ribbons are materials which combine high value of the magnetoimpedance effect (MI), high sensitivity with respect to the applied magnetic field, good corrosion stability in aggressive environments, and reasonably low price. Functional properties of ribbon-based sensitive elements can be modified by deposition of additional magnetic and non-ferromagnetic layers with required conductivity. Such layers can play different roles. In the case of magnetic biosensors for magnetic label detection, they can provide the best conditions for self-assembling processes in biological experiments. In this work, magnetic properties and MI effect were studied for the cases of rapidly quenched Co67Fe3Cr3Si15B12 amorphous ribbons and magnetic Fe20Ni80/Co67Fe3Cr3Si15B12/Fe20Ni80 composites obtained by deposition of Fe20Ni80 1 µm thick films onto both sides of the ribbons by magnetron sputtering technique. Their comparative analysis was used for finite element computer simulations of MI responses with different types of magnetic and conductive coatings. The obtained results can be useful for the design of MI sensor development, including MI biosensors for magnetic label detection.


Assuntos
Técnicas Biossensoriais , Magnetismo , Campos Magnéticos
14.
Nanoscale ; 13(37): 15631-15646, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34596185

RESUMO

The use of magnetic nanoparticles (MNPs) to locally increase the temperature at the nanoscale under the remote application of alternating magnetic fields (magnetic particle hyperthermia, MHT) has become an important subject of nanomedicine multidisciplinary research, focusing among other topics on the optimization of the heating performance of MNPs and their assemblies under the effect of the magnetic field. We report experimental data of heat released by MNPs using a wide range of anisometric shapes and their assemblies in different media. We outline a basic theoretical investigation, which assists the interpretation of the experimental data, including the effect of the size, shape and assembly of MNPs on the MNPs' hysteresis loops and the maximum heat delivered. We report heat release data of anisometric MNPs, including nanodisks, spindles (elongated nanoparticles) and nanocubes, analysing, for a given shape, the size dependence. We study the MNPs either acting as individuals or assembled through a magnetic-field-assisted method. Thus, the physical geometrical arrangement of these anisometric particles, the magnetization switching and the heat release (by means of the determination of the specific adsorption rate, SAR values) under the application of AC fields have been analysed and compared in aqueous suspensions and after immobilization in agar matrix mimicking the tumour environment. The different nano-systems were analysed when dispersed at random or in assembled configurations. We report a systematic fall in the SAR for all anisometric MNPs randomly embedded in a viscous environment. However, certain anisometric shapes will have a less marked, an almost total preservation or even an increase in SAR when embedded in a viscous environment with certain orientation, in contrast to the measurements in water solution. Discrepancies between theoretical and experimental values reflect the complexity of the systems due to the interplay of different factors such as size, shape and nanoparticle assembly due to magnetic interactions. We demonstrate that magnetic assembly holds great potential for producing materials with high functional and structural diversity, as we transform our nanoscale building blocks (anisometric MNPs) into a material displaying enhanced SAR properties.


Assuntos
Hipertermia Induzida , Nanopartículas de Magnetita , Medicamentos de Ervas Chinesas , Humanos , Hipertermia , Campos Magnéticos , Magnetismo
15.
Sensors (Basel) ; 21(19)2021 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-34640685

RESUMO

Magnetometers measure the local magnetic field and are present in most modern inertial measurement units (IMUs). Readings from magnetometers are used to identify Earth's Magnetic North outdoors, but are often ignored during indoor experiments since the magnetic field does not behave how most expect. This paper presents methods to create, validate, and visualize three-dimensional magnetic field maps to expand the use of magnetic fields as a sensing modality for navigation. The utility of these maps is measured in their ability to accurately represent the magnetic field and to enable dynamic attitude estimation. In experiments with motion capture truth data, a small multicopter with three-axis inertial measurements, including magnetometer, traversed five flight profiles distinctly exciting roll, pitch, and yaw motion to provide interesting trajectories for attitude estimation. Indoor experimental results were compared to those outdoors to emphasize how spatial variation in the magnetic field drives the need for our mapping techniques. Our work presents a new way of visualizing 3D magnetic fields, which allows users to better reason about the magnetic field in their workspace. Next, we show that magnetic field maps generated from coverage patterns are generally more accurate, but training such maps using observations from desired flight paths is sufficient in the vicinity of these paths. All training sets were interpolated using Gaussian process regression (GPR), which yielded maps with <1 µT of error when interpolating between and extrapolating outside of observed locations. Finally, we validated the utility of our GPR-based maps in enabling attitude estimates in regions of high magnetic field spatial variation with experimental data.


Assuntos
Algoritmos , Campos Magnéticos , Magnetismo , Movimento (Física) , Distribuição Normal
16.
Sensors (Basel) ; 21(19)2021 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-34640884

RESUMO

Some 175 years ago Michael Faraday discovered magnetic circular birefringence, now commonly known as the Faraday effect. Sensing the magnetic field through the influence that the field has on light within the fiber optic sensor offers several advantages, one of them fundamental. These advantages find application in the measurement of electric current at high voltages by measuring the induced magnetic field, thus warranting application for this kind of fiber optic sensor (FOS) in future smart grids. Difficulties in designing and manufacturing high-performance FOSs were greatly alleviated by developments in optical telecommunication technology, thus giving new impetus to magnetometry based on the Faraday effect. Some of the major problems in the processing of optical signals and temperature dependence have been resolved, yet much effort is still needed to implement all solutions into a single commercial device. Artificial structures with giant Faraday rotation, reported in the literature in the 21st century, will further improve the performance of FOSs based on the Faraday effect. This paper will consider obstacles and limits imposed by the available technology and review solutions proposed so far for fiber optic sensors based on the Faraday effect.


Assuntos
Tecnologia de Fibra Óptica , Campos Magnéticos , Birrefringência , Magnetismo , Rotação
17.
Sensors (Basel) ; 21(19)2021 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-34640915

RESUMO

Traditional fluxgate sensors used in geomagnetic field observations are large, costly, power-consuming and often limited in their use. Although the size of the micro-fluxgate sensors has been significantly reduced, their performance, including indicators such as accuracy and signal-to-noise, does not meet observational requirements. To address these problems, a new race-track type probe is designed based on a magnetic core made of a Co-based amorphous ribbon. The size of this single-component probe is only Φ10 mm × 30 mm. The signal processing circuit is also optimized. The whole size of the sensor integrated with probes and data acquisition module is Φ70 mm × 100 mm. Compared with traditional fluxgate and micro-fluxgate sensors, the designed sensor is compact and provides excellent performance equal to traditional fluxgate sensors with good linearity and RMS noise of less than 0.1 nT. From operational tests, the results are in good agreement with those from a standard fluxgate magnetometer. Being more suitable for modern dense deployment of geomagnetic observations, this small-size fluxgate sensor offers promising research applications at lower costs.


Assuntos
Magnetismo , Processamento de Sinais Assistido por Computador
18.
Sensors (Basel) ; 21(19)2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34640933

RESUMO

Magnetic nanoparticles have been investigated for microwave imaging over the last decade. The use of functionalized magnetic nanoparticles, which are able to accumulate selectively within tumorous tissue, can increase the diagnostic reliability. This paper deals with the detecting and imaging of magnetic nanoparticles by means of ultra-wideband microwave sensing via pseudo-noise technology. The investigations were based on phantom measurements. In the first experiment, we analyzed the detectability of magnetic nanoparticles depending on the magnetic field intensity of the polarizing magnetic field, as well as the viscosity of the target and the surrounding medium in which the particles were embedded, respectively. The results show a nonlinear behavior of the magnetic nanoparticle response depending on the magnetic field intensity for magnetic nanoparticles diluted in distilled water and for magnetic nanoparticles embedded in a solid medium. Furthermore, the maximum amplitude of the magnetic nanoparticles responses varies for the different surrounding materials of the magnetic nanoparticles. In the second experiment, we investigated the influence of the target position on the three-dimensional imaging of the magnetic nanoparticles in a realistic measurement setup for breast cancer imaging. The results show that the magnetic nanoparticles can be detected successfully. However, the intensity of the particles in the image depends on its position due to the path-dependent attenuation, the inhomogeneous microwave illumination of the breast, and the inhomogeneity of the magnetic field. Regarding the last point, we present an approach to compensate for the inhomogeneity of the magnetic field by computing a position-dependent correction factor based on the measured magnetic field intensity and the magnetic susceptibility of the magnetic particles. Moreover, the results indicate an influence of the polarizing magnetic field on the measured ultra-wideband signals even without magnetic nanoparticles. Such a disturbing influence of the polarizing magnetic field on the measurements should be reduced for a robust magnetic nanoparticles detection. Therefore, we analyzed the two-state (ON/OFF) and the sinusoidal modulation of the external magnetic field concerning the detectability of the magnetic nanoparticles with respect to these spurious effects, as well as their practical application.


Assuntos
Nanopartículas de Magnetita , Micro-Ondas , Humanos , Imageamento Tridimensional , Magnetismo , Reprodutibilidade dos Testes
19.
Nano Lett ; 21(20): 8657-8663, 2021 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-34662128

RESUMO

Organic molecules and specifically bio-organic systems are attractive for applications due to their low cost, variability, environmental friendliness, and facile manufacturing in a bottom-up fashion. However, due to their relatively low conductivity, their actual application is very limited. Chiral metallo-bio-organic crystals, on the other hand, have improved conduction and in addition interesting magnetic properties. We developed a spin transistor using these crystals and based on the chiral-induced spin selectivity effect. This device features a memristor type behavior, which depend on trapping both charges and spins. The spin properties are monitored by Hall signal and by an external magnetic field. The spin transistor exhibits nonlinear drain-source currents, with multilevel controlled states generated by the magnetization of the source. Varying the source magnetization enables a six-level readout for the two-terminal device. The simplicity of the device paves the way for its technological application in organic electronics and bioelectronics.


Assuntos
Eletrônica , Magnetismo , Condutividade Elétrica , Campos Magnéticos , Metais
20.
ACS Biomater Sci Eng ; 7(11): 5107-5117, 2021 11 08.
Artigo em Inglês | MEDLINE | ID: mdl-34677934

RESUMO

Cationic magnetic hydrogel microparticles with high retention on cell surfaces were prepared using a two-step procedure. Using these magnetic hydrogel microparticles, cells were clustered with each other, and cell aggregates were prepared effectively. Cross-linked poly(vinyl alcohol) (PVA) hydrogel microparticles containing iron oxide nanoparticles were prepared. The diameter of the microparticles was in the range of 200-500 nm. Water-soluble cationic polymers containing both trimethyl ammonium (TMA) groups and phenylboronic acid (PBA) groups were synthesized for the surface modification of the microparticles. To regulate the composition, electrically neutral phosphorylcholine groups were introduced into the polymer. Covalent bonds were formed between the hydroxy groups of PVA microparticles and PBA groups in the polymer. The surface zeta potential of the microparticles reflected the composition of the TMA groups. The particles responded to an external magnetic field and clustered rapidly. Microparticles were adsorbed on the floating cell surface and induced cell aggregation quickly when a magnetic field was applied. Under the most effective conditions, the diameter of the cell aggregates increased to approximately 1 mm after 30 min. Denser cell aggregates were formed by the synergistic effects of the magnetic field and the properties of the microparticles. The formed cell aggregates continued to grow for more than 4 days under an applied magnetic field, indicating that the ability of the cells in the aggregate to proliferate was well maintained.


Assuntos
Hidrogéis , Polímeros , Fenômenos Magnéticos , Magnetismo , Álcool de Polivinil
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