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We investigated femto- and picosecond-time magnetization dynamics in a ferromagnetic Ni80Fe20 film with varying thicknesses (wedge-shaped film). We observed that the thickness gradient strongly affects the magnetic moment distribution, causing a magnetization reorientation from in-plane to out-of-plane, and formatting a stripe domain (SD) at the thicker end of the wedge. The magnetization dynamics measurements reveal that the part of the film displaying SDs follows a substantially faster demagnetization and magnetization recovery and smaller magnetization quenching compared to the in-plane domain film. The experiments and micromagnetic simulations support that the decrease in relaxation time is caused by a magnetic anisotropy of the films introduced by SD formation. Our results point out that the micromagnetic structure plays an important role in the magnetization dynamics in ferromagnetic films after optically triggered demagnetization.

We report the rotatable anisotropy in three magnetic film systems, including in-plane magnetized FeNi film, FeNi/FeMn bilayer and FeNi stripe domains (SDs) structure film. Omnidirectional ferromagnetic resonance driven by rotatable anisotropy can be achieved in these films. We have found that the in-plane magnetized FeNi films have a negligible rotatable anisotropy of about 1 ∼ 2 Oe. Rotatable anisotropy fields of 6.1 Oe and 5.5 Oe are found for isotropic and anisotropic FeNi/FeMn bilayers, which comes from the exchange coupling at the interface of FM and AFM layer. This magnitude is smaller than the value found in thick FeNi film where a big rotatable anisotropy field of 87 Oe is present stemming from its domain structure. In addition, the uniaxial anisotropy could tailor the resonance frequency from 0.78 and 2.28 GHz for in-plane magnetized FeNi thin film, and 1.3 to 2.4 GHz for FeNi SDs films. Furthermore, a conclusion that a uniaxial anisotropy has no influence on rotatable anisotropy in three magnetic films systems, was yielded.

The ascending prevalence of obesity in recent decades is commonly associated with soaring morbidity and mortality rates, resulting in increased health-care costs and decreased quality of life. A systemic state of stress characterized by low-grade inflammation and pathological formation of reactive oxygen species (ROS) usually manifests in obesity. The transcription factor nuclear factor erythroid-derived 2-like 2 (NRF2) is the master regulator of the redox homeostasis and plays a critical role in the resolution of inflammation. Here, we show that the natural isothiocyanate and potent NRF2 activator sulforaphane reverses diet-induced obesity through a predominantly, but not exclusively, NRF2-dependent mechanism that requires a functional leptin receptor signaling and hyperleptinemia. Sulforaphane does not reduce the body weight or food intake of lean mice but induces an anorectic response when coadministered with exogenous leptin. Leptin-deficient Lepob/ob mice and leptin receptor mutant Leprdb/db mice display resistance to the weight-reducing effect of sulforaphane, supporting the conclusion that the antiobesity effect of sulforaphane requires functional leptin receptor signaling. Furthermore, our results suggest the skeletal muscle as the most notable site of action of sulforaphane whose peripheral NRF2 action signals to alleviate leptin resistance. Transcriptional profiling of six major metabolically relevant tissues highlights that sulforaphane suppresses fatty acid synthesis while promoting ribosome biogenesis, reducing ROS accumulation, and resolving inflammation, therefore representing a unique transcriptional program that leads to protection from obesity. Our findings argue for clinical evaluation of sulforaphane for weight loss and obesity-associated metabolic disorders.

Flavour additives with carboxyl and hydroxyl groups (FACHs), the key ingredients in characteristic flavours, are frequently detected in cigarette smoke. They are attracting increasing attention in regulating the flavour additives used in tobacco to curb youth tobacco use and prevent the use of additives that are harmful. In this study, a highly robust, sensitive, and precise method based on silylation and GC-MS/MS with an improved backflushing system was developed for the simultaneous analysis of 171 FACHs in cigarette smoke. Silylation has been shown to have advantages in terms of high selectivity and sensitivity to chemicals with carboxyl and hydroxyl groups, especially when combined with GC-MS/MS. The extraction and silylation conditions were optimised. Dichloromethane was used as the extraction agent. BSTFA in combination with 1% TMCS and 0.2% TMSI was selected as silylating agent for high silylation efficiency, particularly for hindered analytes. The method has been validated. The limit of detection (LOD) ranged from 0.6 to 332.3 ng/mL. 91.1% out of the analytes in QC samples had precisions lower than 10% during one month run. The improved backflushing system with a fused silica splitter was shown to be crucial in the excellent long-term robustness of the method. The developed method was used to determine flavour additives in 270 practical cigarette smoke samples with reliable results. A total of 154 FACHs were identified with wide-range levels among different cigarette brands.

Hypothalamic regulation of feeding and energy expenditure is a fundamental and evolutionarily conserved neurophysiological process critical for survival. Dysregulation of these processes, due to environmental or genetic causes, can lead to a variety of pathological conditions ranging from obesity to anorexia. Melanocortins and endogenous cannabinoids (eCBs) have been implicated in the regulation of feeding and energy homeostasis; however, the interaction between these signaling systems is poorly understood. Here, we show that the eCB 2-arachidonoylglycerol (2-AG) regulates the activity of melanocortin 4 receptor (MC4R) cells in the paraventricular nucleus of the hypothalamus (PVN(MC4R)) via inhibition of afferent GABAergic drive. Furthermore, the tonicity of eCBs signaling is inversely proportional to energy state, and mice with impaired 2-AG synthesis within MC4R neurons weigh less, are hypophagic, exhibit increased energy expenditure, and are resistant to diet-induced obesity. These mice also exhibit MC4R agonist insensitivity, suggesting that the energy state–dependent, 2-AG-mediated suppression of GABA input modulates PVN(MC4R) neuron activity to effectively respond to the MC4R natural ligands to regulate energy homeostasis. Furthermore, post-developmental disruption of PVN 2-AG synthesis results in hypophagia and death. These findings illustrate a functional interaction at the cellular level between two fundamental regulators of energy homeostasis, the melanocortin and eCB signaling pathways in the hypothalamic feeding circuitry.

The magnetic heterostructures, consisting of Fe nanowire arrays (FNWs) and Fe25Ni75 film, are prepared by combining electrochemical deposition and RF magnetron sputtering. The ferromagnetic resonance (FMR) property in the magnetic heterostructures is investigated by using frequency sweep mode and field sweep mode. The results of hysteresis loops and permeability spectra indicate that the FNWs could destroy the stripe domain structure in Fe25Ni75 film. The resonance absorption near the FMR field is excited in the heterostructures, which can be attributed to the spin non-uniform precession namely spin waves resonance excitation.

FeNi films with different phase structures were prepared by electrodeposition method, and the phase structure of the film was controlled by the composition of the film. The results indicated that the well-defined stripe domain patterns and good magnetic properties of the films were fond of the bcc and bcc + fcc phase structures of the FeNi films. The results of permeability spectra indicated that the acoustic and optical modes of the film could be changed by the direction of the microwave field and stripe domain. FeNi stripe domain films exhibited the different frequency under the two modes, and the acoustic and optical modes of film showed obvious spectra in the bcc and bcc + fcc phases of FeNi films. The results are helpful to the development of the stripe domain optical mode microwave devices.

Leptin signals to regulate food intake and energy expenditure under conditions of normative energy homeostasis. The central expression and function of leptin receptor B (LepRb) have been extensively studied during the past two decades; however, the mechanisms by which LepRb signaling dysregulation contributes to the pathophysiology of obesity remains unclear. The paraventricular nucleus of the hypothalamus (PVN) plays a crucial role in regulating energy balance as well as the neuroendocrine axes. The role of LepRb expression in the PVN in regard to the regulation of physiological function of leptin has been controversial. The single-minded homolog 1 gene (Sim1) is densely expressed in the PVN and in parts of the amygdala, making Sim1-Cre mice a useful model for examining molecular mechanisms regulating PVN function. In this study, we characterized the physiological role of LepRb in Sim1-expressing neurons using LepRb-floxed × Sim1-Cre mice. Sim1-specific LepRb-deficient mice were surprisingly hypophagic on regular chow but gained more weight upon exposure to a high-fat diet than did their control littermates. We show that Sim1-specific deletion of a single LepRb gene copy caused decreased surface and core body temperatures as well as decreased energy expenditure in ambient room temperatures in both female and male mice. Furthermore, cold-induced adaptive (nonshivering) thermogenesis is disrupted in homozygous knockout mice. A defective thermoregulatory response was associated with defective cold-induced upregulation of uncoupling protein 1 in brown adipose tissue and reduced serum T4. Our study provides novel functional evidence supporting LepRb signaling in Sim1 neurons in the regulation of body weight, core body temperature, and cold-induced adaptive thermogenesis.

The microstructure and electro-magnetic properties of FeCoHfN thin films deposited by reactive sputtering under an in-situ magnetic field have been studied as a function of nitrogen partial pressure (R(N2)). As the (R(N2)) increases, the grain size of α-FeCo phase can be effectively reduced, and the structure of the films changes from an amorphous/nanocrystalline dual-phase structure with ultrafine α-FeCo magnetic nanoparticles isolated by a nonmagnetic insulating layer to a single amorphous structure. The structural transformation and the enrichment of HfN layer improve the resistivity and static and dynamic soft magnetic properties of the films. Higher resistivity is expected to reduce eddy current losses at high frequencies. The critical (R(N2)) when the film shows indications of excellent high-frequency magnetic properties is 8%. The deposited FeCoHfN thin films have high saturation magnetization of 14.9-16.2 kGs, great permeability of 222-322 at GHz, and high ferromagnetic resonance frequency up to 3.5 GHz, showing the promise of high-frequency applications.

Magnetic carbon composite (Fe

The adipose tissue-derived hormone leptin can drive decreases in food intake while increasing energy expenditure. In diet-induced obesity, circulating leptin levels rise proportionally to adiposity. Despite this hyperleptinemia, rodents and humans with obesity maintain increased adiposity and are resistant to leptin's actions. Here we show that inhibitors of the cytosolic enzyme histone deacetylase 6 (HDAC6) act as potent leptin sensitizers and anti-obesity agents in diet-induced obese mice. Specifically, HDAC6 inhibitors, such as tubastatin A, reduce food intake, fat mass, hepatic steatosis and improve systemic glucose homeostasis in an HDAC6-dependent manner. Mechanistically, peripheral, but not central, inhibition of HDAC6 confers central leptin sensitivity. Additionally, the anti-obesity effect of tubastatin A is attenuated in animals with a defective central leptin-melanocortin circuitry, including db/db and MC4R knockout mice. Our results suggest the existence of an HDAC6-regulated adipokine that serves as a leptin-sensitizing agent and reveals HDAC6 as a potential target for the treatment of obesity.

In this paper, a serious of CoFeB films of 30 nm prepared by a DC magnetron sputtering on Si substrates with different roughness etched by NaOH solution are investigated. It is found that the coercivity (H-c) and effective damping coefficient alpha are influenced by the substrate roughness of the films. As the substrate roughness increased to 73.9 nm, the H-c ranged from 14.4 Oe to 81.4 Oe; the alpha, from 0.012 to 0.11 at the same time. It is attributed to the function of magnetic moment pinning and magnon-magnon scattering caused by the rough substrate. Thus, the tunable performances of soft magnetism and high frequency of CoFeB films make them become potential candidates for microwave-based devices and other tunable microwave devices. (C) 2018 Elsevier B.V. All rights reserved.

Periodic micro-stripes arrays with stripe domains structures upon continuous permalloy (Py) film were fabricated by sputtering, photolithography and ion beam etching technology. These samples display in-plane magnetic anisotropy, and stripe domains structure is observed by the magnetic force microscopy (MFM) in the area of the micro-stripes. The periodic micro-stripes show an effective impact on static and dynamic magnetic properties of Py continuous film. In the case of dynamic magnetic properties, the resonance frequency fr of these samples can be tuned by periodic micro-stripes arrays. Compared to continuous film with resonance frequency fr of 0.64 GHz, the fr of composite structures can be tuned by the separation gap of periodic micro-stripes arrays from 0.8 GHz to 2.3 GHz at zero-field. At the same time, the fr could be also tuned by rotating the samples within the plane. This attributes to the competition of shape anisotropy induced by micro-stripes and the dynamic anisotropy originating by stripe domains structure.

A new supramolecular host-bonded stationary phase for high-performance liquid chromatography (HPLC) was prepared by coupling a 26-membered aromatic-aliphatic-mixed azamacrocycle to 3-chloropropyltrimethoxylsilane-modified silica, which was characterized by infrared spectroscopy and elemental analysis. To understand the role of functional groups and the nano-sized cavity on the azamacrocycle for its chromatographic performance, the chromatographic behavior of the new stationary phase was investigated by using alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs), aromatic amines, and aromatic positional isomers as probes. This stationary phase exhibited a unique chromatographic retention, which was characterized by multiple interactions between the stationary phase and analytes, including hydrophobic, π–π, hydrogen-bonding, and inclusion interactions. At the same time, the embedded azamacrocycle showed remarkable superiority over the C18 phase in terms of shape, planarity, and isomeric recognition in discriminating specific PAHs and isomers and overcoming the negative effect of residual silanol groups. Such a hybrid stationary phase is more versatile and shows great potential in the analysis of complex samples.

The influence of cycle rapid cooling treatment on the giant magnetoimpedance (GMI) properties in Co-based amorphous alloys was investigated. Hysteresis loops show that the saturation magnetization of ribbons has been improved by cycle treatment. It can be found that the GMI ratio was increased from 89% to 130% at 1 MHz by the thermal cycle (TC) treatment. Moreover, GMI ratio of TC treatment sample increased up to 321% at 5 MHz. It is considered that internal thermoelastic stress leads to surface roughness, magnetic domain structures and saturation magnetization changes of the ribbons during different cycle processes. It was also found that the asymmetric GMI (AGMI) phenomenon occurred in the Co-based alloys with TC treatment after annealing, which can be regarded as a new method to get GMI-valve to improve GMI sensitivity.

The magnetic properties of various samples were investigated through vibrating sample magnetometer, electron spin resonance (ESR), and vector network analyzer ferromagnetic resonance (VNA-FMR) techniques, respectively. The corresponding saturation magnetization $4\pi M_{s}$ and in-plane magnetic anisotropy field $H_{k}$ of those different films were estimated by the three methods. A comparative investigation of the three techniques, especially for ESR and VNA-FMR, on the estimation of $4\pi M_{s}$ and $H_{k}$ was analyzed systematically. The influence of omitted $H_{k}$ on the data of $4\pi M_{s}$ and $H_{k}$ was also studied. The results provide a quite clear conclusion for the measurements of $4\pi M_{s}$ and $H_{\mathbf {k}}$ in different conditions.

NiFe2−xCexO4 (x = 0–0.03) nanoribbons have been successfully fabricated using electrospinning technique and followed by calcining in air at 500 °C. The crystalline, morphologies and compositions of NiFe2−xCexO4 nanoribbons are characterized by X-ray diffraction, selected area electron diffraction, transmission electron microscope, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX). The results show that the components, mean crystallite sizes and morphologies change along with the content of Ce3+. A formation mechanism of NiFe2-xCexO4 nanoribbons is proposed. The magnetic hysteresis loops of NiFe2−xCexO4 nanoribbons reveals that the coercivity changes from 165 Oe to 64 Oe and saturation magnetizations change from 40.97 emu/g to 25.05 emu/g at room temperature. Morevover, the Mossbauer spectra of 57Fe in NiFe2−xCexO4 nanoribbons is discussed in detail. It is believed that this work will play important role in magnetic application with the advantage of excellent magnetic properties, efficient functionalization and relatively low cost.

The present work describes the fabrication of yttrium iron garnet (YIG) nanofibers prepared via electrospinning method. The YIG nanofibers with diameters of around 80 nm were formed when calcinations temperature exceeded 750 °C. The morphology and magnetic parameters including saturation magnetization ( M s ) and coercivity ( H c ) of these samples dramatically change with variation of the annealing temperature. In particular, the M s displays a steady increase from 3.1 emu/g at 700–21.5 emu/g at 1000 °C, and the H c shows a different tendency that first increases to a maximum value of 140 Oe at 750 °C, and then reduce distinctly. Finally, the electron spin resonance spectra display strong asymmetry and broad linewidth that are highly affected by shape anisotropy, defects and the presence of trace amount second phase orthorhombic YFeO 3 ( o -YFeO 3 ) in the YIG nanofibers.

Nanowire/Permalloy (Ni 80 Fe 20 ) composite films were fabricated by combined electrospinning and sputtering. The magnetic properties of the composite films are isotropic in-plane. Stripe domains were characterized by magnetic force microscopy and vector-network-analyzer ferromagnetic resonance. Compared with pure Permalloy films with distinct stripe domains, the composite films have weaker stripe domains but better soft magnetic properties. The coercivity and dynamic anisotropy fields are 47 Oe and 73 Oe, respectively, for pure Permalloy, decreasing to 23 Oe and 67 Oe, respectively, for the Fe-Ni nanowire/Permalloy composite film. Composite films provide new insight on the improvement of the soft magnetic properties of magnetic films.

FeCo films were synthesized by electrodeposition method with a magnetic field applied parallel to the plane of the film. The microstructure as well as the dynamic magnetic properties of the films has been studied as a function of the film thickness, which was varied from 82 nm to 1756 nm. In-plane anisotropy field and saturation magnetization of the film were estimated by ferromagnetic resonance spectra and electron spin resonance spectra. Both of the two results show the in-plane anisotropy field is increased with the improvement of film thickness. The saturation magnetization of film displays no obvious change with the increased thickness. In addition, the damping of the FeCo film is significantly changed with the improvement of film thickness, but it is almost constant in the case of thicker thickness.

FeNi films with the stripe domain (SD) pattern are prepared by electrodeposition and sputtering methods. The magnetic domain, static magnetic parameters, and quality factor, as well as dynamic properties of the two films, are respectively performed. The results show the magnetizations of the film were dependent on the direction of SD, and the rotation of the SD is lagging behind the magnetization reversal. The microwave properties of the SD emerge dynamic hysteresis before the saturation magnetic field. These microwave properties are selectively excited with acoustic mode, optical mode, and spin-wave mode. The frequency and intensity of different resonance modes of stripe domain are determined by the local magnetization. The magnetization variations and the rotation of SD of different modes are further illuminated by the micromagnetic simulation. The magnetic anisotropy and the resonance intensity of permeability of different modes were finally described by the modified resonance equations., 10 pages, 9 figures

FeCo films were prepared by a simple and convenient electrodeposition method. An external magnetic field was applied to the film to induce magnetic anisotropy during deposition. Comparing with the previous work, the angle between the direction of applied magnetic field and film plane is changed from in-plane to out-plane. The influence of the applied magnetic field on magnetic properties was investigated. As a result, it can be found that the in-plane anisotropy is driven by the in-plane component of the magnetic field applied during growth. In addition, the result can also be confirmed by the dynamic magnetic anisotropy of the film obtained by vector network analyzer ferromagnetic resonance technique.

We have demonstrated a facile method to synthesize a number of spinel ferrite nano-granules in dimethyl formamide (DMF) through a calcination process under air. There is no pH regulation, gas atmosphere, centrifugation, supplementary reagents, or other complicated and cumbersome procedures during the preparing process. The structures, morphologies, and magnetic properties of NiFe2O4, CoFe2O4, and NiZnFe2O4 nano-granules in various DMF concentrations and different calcination temperatures were investigated systematically, and other MFe2O4 nano-granules were also investigated by this method. As a result, it will cause an impurity phase at low DMF concentration or low calcination temperature, and large quantities of uniform nano-granules will be achieved at about 680 °C in pure DMF. The results show that the method realizes a simple, rapid and convenient route for assembling unitary and binary spinel ferrite nano-granules. In addition, the formation mechanism of the nano-granules was also studied in detail, and DMF plays a dispersing and covering role during the reaction. This synthetic approach also shows great potentiality in the synthesis of maghemite γ-Fe2O3 with high saturation magnetization, and rare nonmetal-doped CoFe2O4 is prepared using this strategy. Magnetic properties of doped CoFe2O4 nano-granules are also improved. These results provide a convenient way for the advancement of magnetic nanomaterials.