M-type hexagonal barium ferrites Ba(M x Ti x )Fe 12-2 x O 19 (M = Co or Zn, x = 0-0.5) were synthesized by chemical topotactical reaction. Both randomly oriented and self-polarized samples were ...prepared. Experimental values of the anisotropy fields, first and second anisotropy constants, and remanent magnetizations were extracted by combining hysteresis loops and microwave measurements. A salient result of this study is that, compared with K 1 , K 2 cannot be disregarded for these co-doped BaM hexaferrites, even at low doping levels. Results show that the BaM ferrites of composition Ba(Co x Ti x )Fe 12-2 x O 19 are more suitable for microwave applications that operate at frequencies between 30 GHz and 40 GHz.
This work investigates electromagnetic properties of half-dense ceramics with compositions Ni0.5Zn0.3Co0.2FeyO4-δ where y=1.98 (Iron deficient, noted ID) or y=2.3 (Iron in excess, noted IE). IE and ...ID materials are obtained by chemical coprecipitation route. The obtained nano-sized powders are pressed and annealed at two temperatures (800°C, 900°C), so has to obtain half-massive ceramics. Ferrous and ferric ions coexist in the crystalline structures, but the former in a less extend for ID ferrite. The concomitant influences of Fe2+ and Fe3+ on the dielectric and magnetic losses (ε″/ε′ and µ″/µ′, respectively) are considered at frequency up to 6GHz. The permeability dispersion changes from relaxation-like to resonance-like with the decrease in ferrous ions. In reason of the relaxing-like behavior of Fe2+, and because of a relatively high amount in Fe2+, IE sample shows lower total losses (magnetic and dielectric) than ID sample. These conclusions applied for TA=900°C. At frequencies above 700MHz, the total loss values (IE and ID samples) are prohibitive for antenna downsizing whatever is the firing temperature value (800°C and 900°C). Whereas at frequencies below 700MHz Ni0.5Zn0.3Co0.2Fe2.3O4+δ may leads to better antenna performances than Ni0.5Zn0.3Co0.2Fe1.98O4-δ.
This study presents the performance of a magneto-dielectric material (MDM) specially developed to enable the tunability of antenna devices operating in the VHF band. A current flowing through the ...sample, which creates a DC magnetic field inside the sample with the same symmetry as the magnetic domains, controls the magnetic susceptibility variation of the MDM. By changing the magnetization state of the MDM with a low DC magnetic field of 740 A.m-1, a tunability of 40% can be observed. The MDM tunability at VHF frequencies is also highlighted by microwave measurements for different magnetization states.
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•Nano composites of hard and soft ferrite were synthesized.•Sustained value of permittivity and permeability value are obtained up to mid UHF band.•Ferromagnetic resonance extends ...above 1GHz enabling high operational range of frequencies.•Matching value of permittivity and permeability (both close to 4.6) obtained up to 600MHz.•Design shows better impedance matching and 55% area reduction.
Miniaturization of patch antenna using composite ferrite (Ni0.5Zn0.3Co0.2Fe2O4+BaFe12O19) is proposed in this paper. Substrate material was prepared using a wet chemical method and characterized for its structural and electromagnetic properties. Matching values of complex permittivity (ε*=4.5+0.1j) and complex permeability (μ*=4.6+0.3j) at 500MHz were obtained from the electromagnetic characterization. Simulation result showed that matching and greater than unity value of both permittivity and permeability can reduce the size of antenna by almost 55%. Normalized characteristic impedance close to unity (∼1.022) was observed in the synthesized nano ferrite composites. This results in better impedance matching of the substrate with the surrounding space. Reflection loss was found to decrease (from −28dB to −35dB) and bandwidth increases (1.6–6%) over pure dielectric substrate. Therefore, composite ferrite is proposed as suitable candidate for effective miniaturization of antenna in microwave frequency range.
Currently, very few studies are available concerning the mammalian Hippo pathway in bone sarcomas. YAP/TAZ transcription co-activators are key downstream effectors of this pathway and may also have ...oncogenic properties. Additionally, recent in-vitro experiments showed that expression of β1-integrin promoted metastasis in osteosarcomas. This study investigated the expression of YAP/TAZ and β1-integrin in human osteosarcomas.
We performed automated immunohistochemistry on tissue-microarrays (TMA) in which 69 conventional osteosarcomas biopsies performed prior to chemotherapy were embedded. Cellular localization and semi-quantitative analysis of each immunostain was performed using Immunoreactive Score (IRS) and correlated to clinico-pathological data.
Cytoplasmic expression of β1-integrin was noted in 54/59 osteosarcomas (92%), with 33/59 cases (56%) displaying membranous staining. YAP/TAZ was expressed in 27/45 osteosarcomas (60%), with 14 cases (31%) showing cytoplasmic expression while 13 other cases (28%) displayed nuclear expression. No link was found between YAP/TAZ or β1-integrin expression and response to chemotherapy. In univariate analysis, YAP/TAZ immunoreactive score was pejoratively correlated with overall survival (p = 0.01). Expression of β1-integrin on cell membrane was also pejorative for OS (p = 0.045). In multivariate analysis, YAP/TAZ nuclear expression was an independent prognostic factor for PFS (p = 0.035).
this study indicates that β1-integrin and YAP/TAZ proteins are linked to prognosis and therefore could be therapeutic targets in conventional osteosarcomas.
This study is aimed at the manufacture and the magnetic properties of polycrystalline M-type hexaferrites BaFe12O19 (barium ferrite, or BaM) materials of different magnetic texturing grades, going ...from a random distribution of the BaM crystallites to their almost complete stacking. Our target is to optimize the value of reduced-remanence magnetization MR/MS, which is among the most significant features of the self-polarized materials. In this study, we focus on the role played by the precursors hematite (isotropic spherical shape) and goethite (anisotropic lath shape). Therefore, 11 samples with a flat cylinder shape are fabricated, with an increasing hematite to goethite ratio. We demonstrate that this ratio drives the texturization of the samples by producing self-polarized materials with different MR/MS from the simple green compaction of the precursors, followed by a heat treatment. Most importantly, our study reveals the orientation of BaM particles after compaction; therefore, MR/MS, is strongly influenced by the aspect ratio of the lath-shaped goethite crystallites. Additionally, we show that finer goethite crystallites yield higher-value MR/MS. We optimize the aspect ratio of the goethite crystallites for an improved BaM texture. The optimization of the morphology of the goethite crystallites leads to an increase in the BaM particles’ orientation and stacking. The salient outcome of this work, which distinguishes it significantly from recent works, is that the particles stacking increases with the value of the shape factor η (defined as the ratio of the diameter of the laths to their length) of the goethite, evidenced by XRD results. The Rietveld refinements of powder diffractograms and the measured magnetic properties reveal a particle-stacking enhancement caused by not only the ratio of hematite: goethite but mainly by an optimal aspect ratio of the goethite crystallites. Based on this study, the BaM materials are further manufactured with a controlled magnetic texture; thus, they are partly self-polarized. They show reduced-remanence magnetization MR/MS varying from 0.5 and 0.81, while the angular dispersion of the BaM particles’ easy axis of magnetization varies from 60° to 10°. The magnetic properties of the samples are further studied in microwave experiments, from which the value of the magnetocrystalline anisotropy field HK = 16.6 kOe is deduced. The first magnetization curves of each sample are obtained using a VSM. A law of approach to the saturation suitable for the case of the uniaxial polycrystalline materials, and for which the particle stacking is only partial, is proposed for the fitting of the magnetization process. It is suggested that by using the proposed law with a known magnetocrystalline anisotropy constant K1, the angular grain-dispersion can be found.
This paper presents an ultracompact antenna design suited for digital video broadcasting-handheld (DVB-H) reception devices. The DVB-H frequency band is ranging from 4 70 to 862 MHz and divided in 49 ...channels of 8 MHz. Designed to be integrated in a tablet, it is not only heavily miniaturized (λ 0 /49 × λ 0 /71 ×λ 0 /160 at 470 MHz), but also able to cover each channel thanks to the use of a magneto-dielectric material. The advantage of using such a material is studied and described in this paper. Moreover, the operating frequency is continuously tuned over the whole DVB-H band by the integration of a varactor diode. This varactor diode has been characterized and modeled to properly cosimulate its behavior within the antenna. Limitations in terms of accepted power by the diode are emphasizing. Finally, the antenna design, including both magneto-dielectric material and varactor diode is integrated in the DVB-H receiver device. Measurement performances are presented and discussed.
This study investigates the magnetocrystalline anisotropy constants (K1) and the saturation magnetostriction constants (λS) of Ni1−xZnxFe2O4 (NiZn) and Ni0.8−xZnxCo0.2Fe1.98O4−δ (NiZnCo) ferrites ...intended to be used for antenna downsizing. Composite materials constituted of soft ferrite nanosized particles (NiZn or NiZnCo ferrites) embedded in an epoxy matrix are realized. Measurements of their magnetic permeability in the frequency range of 200MHz–6GHz are performed. The influence of compressive stress (in the range of 32–96MPa) on their Ferrimagnetic Resonance (FMR) is demonstrated. An analytical modeling of stress-induced FMR changes is proposed that allows simultaneous determinations of the Natural Ferrimagnetic Resonance (NFMR, F0), K1 and λS of Ni1−xZnxFe2O4 and Ni0.8−xZnxCo0.2Fe1.98O4−δ ferrites. The obtained results for NiZn ferrites are in agreement with literature data, validating both the experimental process and the proposed modeling of the stress-induced FMR changes. Regarding NiZnCo ferrites, extended data on K1 and λS are presented for the first time. Increasing zinc content (x) induces a spin disorder that reduces in a same time K1 and the magnetization at saturation MS. The rapid variation of K1(x) is related to that of the magnetization MS(x) through a power law. The single-ion anisotropy model allows a satisfactory interpretation of K1 dependence on zinc content. The unexpected low values of λS got for NiZnCo ferrites, compared to those got for NiZn ferrites, are also discussed. Application of compressive stress lowers noticeably magnetic losses of Ni0.6Zn0.2Co0.2Fe1.98O4−δ at given frequency, thereby enhancing the ability of this spinel ferrite to be used as a substrate in the aim of antenna miniaturization.
•We measure permeability of ferrite-based composites from 0.1GHz to 6GHz.•The influence of compressive stress on the FMR of ferrite-based composites is shown.•Magnetocrystalline constants of NiZn and NiZnCo ferrites are determined.•Magnetostriction constants of NiZn and NiZnCo ferrites are determined.•We show the ability of NiZnCo ferrites to be used for antenna miniaturization.
A series of cobalt substituted lithium ferrite Li0.5CoxFe2.5−xO4 with x=0, 0.2, 0.4 was prepared by a chemical technique called citrate precursor method. In this technique citric acid was used as a ...reducing agent. Structural, morphological, topographical, optical, electrical, and magnetic properties were studied by using X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, DC resistivity, Mössbauer Spectroscopy. XRD patterns showed characteristic (220), (311), (400), (422), (511), (440) peaks which confirmed the inverse spinel phase. SEM and TEM support the formation of cubic nanoparticles. FTIR studies reported the ferrite peaks between 400cm−1 and 800cm−1 confirming the inverse spinel structure. Five optical Raman modes (A1g+Eg+3F2g), characteristics of the cubic spinel structure with (P4332) space group are also observed. Electrical DC resistivity studied from room temperature to 300°C showed the semiconducting behavior of lithium ferrite. Porosity, transition temperature and activation energy are found to decrease with cobalt ion concentration. The room temperature Mössbauer spectra of all the samples showed normal Zeeman Splitting sextets supporting the formation of ferromagnetic phase. With increase in cobalt content, the value of hyperfine field at A site is found to vary from 53.15 to 54.96T whereas at B site it vary from 54.79 to 52.82T. The obtained results have been explained based on possible mechanisms, models and theories.
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•XRD studies confirmed the spinel structure.•In FTIR studies, two frequency metal oxide bands are observed.•Raman spectra confirmed the symmetric and anti-symmetric band position.•Mössbauer spectroscopy reveals the two magnetic sextets.
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