This study aims to investigate the impact of middle ear effusion(MEE)on sound transmission in the human ear and its potential diagnostic significance.Firstly,the material properties of specific structures were adjuste...This study aims to investigate the impact of middle ear effusion(MEE)on sound transmission in the human ear and its potential diagnostic significance.Firstly,the material properties of specific structures were adjusted based on the existing human ear finite element(FE)model,and the accuracy of the model was validated using experimental data.Secondly,six FE models were developed to simulate varying degrees of MEE by systematically altering the material properties of the middle ear cavity(MEC)at different anatomical locations.Finally,the effects of these six FE models,representing varying degrees of MEE,on sound transmission characteristics and energy absorption(EA)rate in the human ear were systematically analyzed.When the degree of MEE is less than 50%of the MEC volume,its impact on the sound transmission characteristics of the human ear remains minimal,resulting in an estimated hearing loss of approximately 3 dB,with EA rate remaining close to normal levels.Once the effusion exceeds 50%of the MEC volume,a significant deterioration in acoustic transmission is observed,accompanied by a flattening of the EA curve and a drop in EA rates to below 20%.When the effusion completely fills the MEC,the maximum hearing loss reaches 46.47 dB,and the EA rate approaches zero across the entire frequency range.These findings provide theoretical insights into the biomechanical effects of MEE on human auditory transmission and offer a reference for clinical diagnosis and evaluation.展开更多
A patented kinetic uricase method was evaluated for serum uric acid assay. Initial absorbance of the reaction mixture before uricase action （A0） was obtained by correcting the absorbance at 293 nm measured before th...A patented kinetic uricase method was evaluated for serum uric acid assay. Initial absorbance of the reaction mixture before uricase action （A0） was obtained by correcting the absorbance at 293 nm measured before the addition of uricase solution, and background absorbance （Ab） was predicted by an integrated method. Uric acid concentration in reaction solution was calculated from AA, the difference between A0 and Ab, using the absorptivity preset for uric acid. This kinetic uricase method exhibited CV〈4.3% and recovery of 100%. Lipids, bilirubin, hemoglobin, ascorbic acid, reduced glutathione and xanthine 〈0.32 mmol/L in serum had no significant effects. △A linearly responded to 1.2 to 37.5 μmol/L uric acid in reaction solution containing 15 μl serum. The slope of linear response was consistent with the absorptivity preset for uric acid while the intercept was consistent with that for serum alone. Uric acid concentrations in clinic sera by different uricase methods positively correlated to each other. By Bland-Altman analysis, this kinetic uricase method accorded with that by quantifying the total change of UV absorbance on the completion of uricase reaction. These results demonstrated that this kinetic uricase method is reliable for serum uric acid assay with enhanced resistance to both xanthine and other common errors, wider range of linear response and much lower cost.展开更多
We derive the expressions of the first and second harmonic signals on the basis of absorption spectral and lock-in theories, and determine the gas concentration according to the ratio of second and first harmonic sign...We derive the expressions of the first and second harmonic signals on the basis of absorption spectral and lock-in theories, and determine the gas concentration according to the ratio of second and first harmonic signals. It is found that the X and Y components of the harmonic signals are influenced by the phase shift between the detection and reference signal, and the phase shift can be any value in a range from 0 to 2π, which is different from the results obtained previously. Meanwhile, an additional item caused by the residual amplitude modulation will make a great contribution to the second harmonic signal, and may not be neglected under low absorbance conditions. Theoretical analysis indicates that subtracting back-ground signal from the second harmonic signal can remove the influence of this item, and can improve the measurement accuracy of gas concentration. On this basis, we select the transition of CO2 at 6527.64 cm-1 to analyse the approximation errors during the derivation by numerical simulation and then measure the CO2 concentration under low absorbance conditions, with absorbance varying from 1‰ to 6‰.展开更多
Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading...Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading pollutants during storage, and its effect on dissolved organic matter（DOM） was investigated in this study. Solar light significantly decreased the UV_（254） absorbance and fluorescence（FLU） intensity of reclaimed water.However, its effect on the dissolved organic carbon（DOC） value of reclaimed water was very limited. The decrease in the UV_（254） absorbance intensity and FLU excitation–emission matrix regional integration volume（FLU volume） of reclaimed water during solar light irradiation was fit with pseudo-first order reaction kinetics. The decrease of UV_（254） absorbance was much slower than that of the FLU volume. Ultraviolet light in solar light had a key role in decreasing the UV_（254） absorbance and FLU intensity during solar light irradiation. The light fluence-based removal kinetic constants of the UV_（254） and FLU intensity were independent of light intensity. The peaks of the UV_（254） absorbance and FLU intensity with an apparent molecular weight（AMW） of 100 Da to 2000 Da decreased after solar irradiation, whereas the DOC value of the major peaks did not significantly change.展开更多
Near-infrared (NIR) spectroscopy was applied to reagent-free quantitative analysis of polysaccharide of a brand product of proprietary Chinese medicine (PCM) oral solution samples. A novel method, called absorbance up...Near-infrared (NIR) spectroscopy was applied to reagent-free quantitative analysis of polysaccharide of a brand product of proprietary Chinese medicine (PCM) oral solution samples. A novel method, called absorbance upper optimization partial least squares (AUO-PLS), was proposed and successfully applied to the wavelength selection. Based on varied partitioning of the calibration and prediction sample sets, the parameter optimization was performed to achieve stability. On the basis of the AUO-PLS method, the selected upper bound of appropriate absorbance was 1.53 and the corresponding wavebands combination was 400 - 1880 & 2088 - 2346 nm. With the use of random validation samples excluded from the modeling process, the root-mean-square error and correlation coefficient of prediction for polysaccharide were 27.09 mg·L<sup>-</sup><sup>1</sup> and 0.888, respectively. The results indicate that the NIR prediction values are close to those of the measured values. NIR spectroscopy combined with AUO-PLS method provided a promising tool for quantification of the polysaccharide for PCM oral solution and this technique is rapid and simple when compared with conventional methods.展开更多
In the article titled“A rapid absorbance-based growth assay to screen the toxicity of oligomer Aβ42 and protect against cell death in yeast”,published on pages 1931–1936,Issue 10,Volume 15 of Neural Regeneration R...In the article titled“A rapid absorbance-based growth assay to screen the toxicity of oligomer Aβ42 and protect against cell death in yeast”,published on pages 1931–1936,Issue 10,Volume 15 of Neural Regeneration Research(Bharadwaj and Martins,2020),there is an error in the title.It should read:A rapid absorbance-based growth assay to screen the toxicity of oligomer Aβ42 and protection against cell death in yeast.展开更多
Five phospholipids in human placenta were determined by phosphorus 31 nuclear magnetic resonance(^(31)P NMR)spectroscopy and thin-layer chromatography(TLC) scanning combined with the corrective method of absorbance pr...Five phospholipids in human placenta were determined by phosphorus 31 nuclear magnetic resonance(^(31)P NMR)spectroscopy and thin-layer chromatography(TLC) scanning combined with the corrective method of absorbance proportional coefficient. The NMR spectrometer used this investigation was a Bruker AM-500 spectrometer operating at 202.4 MHz for ^(31)P chemical shifts are relative to 85% phosphoric acid. TIC was carried out by silica gel H plate developed in chloroform-methanol-glacial acetic acid-ethanol-water(25:4:6:2:0.5),with Vaskovsky reagent as colour -developing agent of phospholipids.展开更多
Objective： To investigate the correlation of fibrinogen level and absorbance change in both PT and APTT clotting curves on BCSXP Analyzer. Methods：A serial of standard fibrinogen and 250 patient plasma samples with ...Objective： To investigate the correlation of fibrinogen level and absorbance change in both PT and APTT clotting curves on BCSXP Analyzer. Methods：A serial of standard fibrinogen and 250 patient plasma samples with different qualities（normal, hemolysis, icterus, and lipemia） were run on BCSXP for assays PT, APTT and Fibrinogen. The absorbance change（DeltaA） from baseline to plateau in clotting curve was retrieved and analyzed on its correlation with the Fibrinogen result. Influence of plasma quality and PT/ APTT result on this correlation was also studied respectively. Results：Both PT-DeltaA and APTT-DeltaA showed good linear regres- sion with fibrinogen level in the sample, with R2 close to 0.90 in both standard and patient samples. Hemolysis（H）, itcterus（I） and lipemia（L） of the sample with valid clotting curves were found to have no significant difference in this correlation from normal（N） sample（R2： 0.83H, 0.92I, 0.81L and 0.79N in PT; 0.89H, 0.95l, 0.91L and 0.89N in APTT） in either PT or APTT curve. PT or APTT result also has little impact on this correlation（0.71 in range 7 - 10 sec, 0.56 inl0 - 20 sec, and 0.70 in 20 sec-; R2 in APTT： 0.88 in 20-30 sec, 0.92 in 30-40 sec, and 0.95 in 40 sec-）. Conclusion：The absorbance change in either PT or APTT clotting curve correlates well with the fibrinogen level in plasma, which is independent of plasma quality PT or APTT results. The absorbance change can be used as an alternative way to roughly estimate fibrinogen level in either PT or APTT clotting curve when the result of clauss-based fibrinogen measurement is not available.展开更多
The optical absorbance in near UV wavelength region in SnO 2 nanoclusters in an external electric field is determined at room temperature. The absorbance spectra as applied field and the absorbance variations with th...The optical absorbance in near UV wavelength region in SnO 2 nanoclusters in an external electric field is determined at room temperature. The absorbance spectra as applied field and the absorbance variations with the applied field are obtained.The relation between absorbance change and applied field is non-linear, and is saturated at high field region.展开更多
In the twenty first century research works, there may be a need to achieve a more reliable research result through a synergy between engineers and biological researchers. The peak absorbance data for various interacti...In the twenty first century research works, there may be a need to achieve a more reliable research result through a synergy between engineers and biological researchers. The peak absorbance data for various interacting systems were measured. These were used to show that the antiretroviral drug has the effect of increasing the peak absorbance values of both the uninfected and infected blood components, i.e., the drugs are made able to increase the light absorption capacity of the blood cells. For drug 2 that contains three components including Efavirenz, the drug effect on lymphocytes was increased by about 38% for patients that had been on antiretroviral drug treatment. Mathematical models were proposed and used in determining the coating effectiveness of antiretroviral drugs in the presence and absence of HIV. The use of the findings of this work by pharmaceutical industries may help in the search for more effective antiretroviral drugs for the treatment of HIV patients.展开更多
Metalorganic chemical vapour deposition (MOCVD) method was used to deposit zinc oxide thin films on soda-lime glass substrates at temperatures of 330°C, 360°C, 390°C and 420°C, using zinc acetate a...Metalorganic chemical vapour deposition (MOCVD) method was used to deposit zinc oxide thin films on soda-lime glass substrates at temperatures of 330°C, 360°C, 390°C and 420°C, using zinc acetate as the precursor. Compressed air was used as the carrier gas at a flow rate of 2.5 dm3 per minute. Each deposition was carried out for two hours under atmospheric pressure. FTIR measurements were subsequently made on the produced thin films to determine their struc ture and trend with deposition temperatures. The measurements showed the presence of lingering functional groups of organic, oxide and nitride origin, which prominently moderated the natural vibrational modes of the material within their respective affiliate wavenumbers, as well as three slight but evident trends in absorbance peaks, cut-off wave length, and the existence of the functional groups with temperature. The produced materials are expected to be useful for enhanced solar cells, triggering sensor devices, p-doped zinc oxide, etc.展开更多
In this work, we present the growth and optical characterization of carbon nanotube/TiO2 anatase nanocomposites. The composites are obtained by doping a bulk of anatase nanometric grains with different weight percenta...In this work, we present the growth and optical characterization of carbon nanotube/TiO2 anatase nanocomposites. The composites are obtained by doping a bulk of anatase nanometric grains with different weight percentages of carbon nanotube (from 0.1% to 50%). We observe that only for tube concentrations between 0.1% and 2%, the growth process shows the formation of a matrix where carbon nanotubes are uniformed and dispersed in a bulk of TiO2 grains. Moreover, the X-ray photoelectron spectroscopy and surface morphology analysis (conducted from AFM images) indicated that the CNT absorption is a simple physisorption without chemical bonds formations between tube and dioxide. Finally, absorption in all the visible range has the increase of about 60% at very low concentration (2%) of carbon nanotubes.展开更多
High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increa...High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorp-tion(EMWA)performance at elevated temperatures,which severely restricts their practical application.In this study,we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide(RGO)/epoxy resin(EP)metacomposites that integrate both electromagnetic parameters and metamaterial design concepts.Due to the discrete distribution of the units,electromagnetic waves can more easily penetrate the interior of materials,thereby exhibiting stable microwave absorption(MA)performance and impedance-matching characteristics suitable across a wide temperature range.Consequently,exceptional MA properties can be achieved within the tem-perature range from 298 to 473 K.Furthermore,by carefully controlling the structural parameters in RGO metacomposites,both the resonant frequency and effective absorption bandwidth(EAB)can be optimized based on precise manipulation of equivalent electromagnetic parameters.This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.展开更多
In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not ...In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.展开更多
Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction...Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood.In this study,we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride(ChCl)and ethylene glycol(EG).Owing to the unique properties of deep eutectic gels,the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded.Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG,with HB-induced conductive loss following similar pat-terns.At a ChCl and EG molar ratio of 2.4,the gel labeled G22-CE2.4 exhibited the best EMW absorption performance,characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm.This superior performance is attributed to the synergistic ef-fects of excellent conductive loss and impedance matching generated by the optimal number of HB.This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.展开更多
With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance elec...With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance electromagnetic wave(EMW)ab-sorbers is an effective method to solve the above issue and has attracted the attention of many researchers.As a typical magnetic material,ferrite plays an important role in the design of high-performance EMW absorbers,and related research focuses on diversified synthesis methods,strong absorption performance,and refined microstructure development.Herein,we focus on the synthesis of ferrites and their composites and introduce recent advances in the high-temperature solid-phase method,sol-gel method,chemical coprecipitation method,and solvent thermal method in the preparation of high-performance EMW absorbers.This review aims to help researchers understand the advantages and disadvantages of ferrite-based EMW absorbers fabricated through these methods.It also provides important guidance and reference for researchers to design high-performance EMW absorption materials based on ferrite.展开更多
Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In t...Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In this study,a flake-like nickel cobaltate/re-duced graphene oxide/melamine-derived carbon foam(FNC/RGO/MDCF)was successfully fabricated through a combination of solvo-thermal treatment and high-temperature pyrolysis.Results indicated that RGO was evenly distributed in the MDCF skeleton,providing ef-fective support for the load growth of FNC on its surface.Sample S3,the FNC/RGO/MDCF composite prepared by solvothermal method for 16 h,exhibited a minimum reflection loss(RL_(min))of-66.44 dB at a thickness of 2.29 mm.When the thickness was reduced to 1.50 mm,the optimal effective absorption bandwidth was 3.84 GHz.Analysis of the absorption mechanism of FNC/RGO/MDCF revealed that its excellent absorption performance was primarily attributed to the combined effects of conduction loss,multiple reflection,scattering,in-terface polarization,and dipole polarization.展开更多
The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.T...The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.This study satisfactorily fabricated a series of MoS_(2)/BN-xyz composites(which were characterized by the weight ratio of MoS_(2)to BN,denoted by xy:z)through chemical vapor depos-ition,which resulted in their improved thermal stability and thermal transmission performance.The results show that the remaining mass of MoS_(2)/BN-101 was as high as 69.25wt%at 800℃under air atmosphere,and a temperature difference of 31.7℃was maintained between the surface temperature and the heating source at a heating temperature of 200℃.Furthermore,MoS_(2)/BN-301 exhibited an im-pressive minimum reflection loss value of-32.21 dB at 4.0 mm and a wide effective attenuation bandwidth ranging from 9.32 to 18.00 GHz(8.68 GHz).Therefore,these simplified synthesized MoS_(2)/BN-xyz composites demonstrate great potential as highly efficient con-tenders for the enhancement of microwave absorption performance and thermal conductance.展开更多
In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-c...In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-cation perovskites(MCPs) have been extensively used as absorber thin films in perovskite solar cells(PSCs), achieving high power conversion efficiencies(PCE) over 26%^([1, 2]).展开更多
[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broad...[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broadband absorbers remains a challenge in terms of practical applications.EMW absorbing materials primarily rely on the magnetic loss of magnetic materials and/or the dielectric loss of dielectric materials to convert EMW energy into thermal energy for dissipation.Among various magnetic materials,Fe_(3)O_(4) plays an irreplaceable role in EMW absorption due to its high saturation magnetization,low cost and compatible dielectric loss in the gigahertz frequency range.Nevertheless,the high density,large matching thickness and narrow absorption bandwidth of Fe_(3)O_(4) pose significant challenges for practical applications.In contrast,one-dimensional(1D)structures not only retain the characteristic properties of lightweight,chemical stability and high dielectric loss,but also exhibit anisotropic structures and large aspect ratios.Additionally,researchers have found that the minimum reflection loss(RL)of hollow carbon materials with mesopores is nearly four times that of non-porous hollow carbon materials and nine times that of dense carbon materials.According to Maxwell's EMW theory,composites consisting of Fe_(3)O_(4) and one-dimensional(1D)mesoporous carbon materials can leverage their respective advantages by optimizing the composition and structure of the composites to balance u,and Er,thereby enhancing EMW absorption performance.Additionally,numerous studies have demonstrated that composites composed of multi-component heterostructures significantly enhance the EAB.This enhancement is primarily ascribed to the numerous interface polarization losses generated by the additional heterostructure interfaces,which also improve the overall impedance matching of the composites.In this study,we leverage the advantages of magnetic/carbon composites,one-dimensional(1D)mesoporous carbon and multi-component heterostructures to prepare a composite of 1D mesoporous carbon-coated manganese oxide(Mn_(3)O_(4) and MnO,denoted as Mn_(x)O_(y))embedded with Fe_(3)0_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4)).This composite was synthesized and its formation mechanism and microstructure were analyzed in detail.At the same time,the influence of this Mn_(x)O_(y)/C@Fe_(3)O_(4) structure on EMW properties and absorbing performance was further discussed.[Methods]Firstly,MnO_(2) nanowires were synthesized by using a simple hydrothermal method.Then,the MnO_(2) nanowires served as templates for the synthesis of MnO_(2)/PDA@Fe^(3+)composites through the in-situ polymerization of dopamine and Fe^(3+)adsorption.Finally,1D mesoporous carbon-coated manganese oxide composite embedded with Fe_(3)O_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4))composites were obtained after heat treatment at 550℃ in N_(2).The crystal structure of the samples was analyzed using X-ray diffractometer with Cu Ka irradiation.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(TEM)were used to observe microstructure and morphology of the samples.Nitrogen sorption measurements were obtained at 77 K on a Quantachrome surface area and pore size analyzer to measure the specific surface area and pore size distribution.XPS analysis was performed on X-ray photoelectron spectrometer with monochromatic Al Ka radiation.Magnetization curves of the samples were recorded with a Quantum Design physical property measurement system(PPMS-9)at room temperature.The electromagnetic parameters of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites were measured using an Agilent N5230C network analyzer in the frequency range of 2-18 GHz.For electromagentic testing,the Mn,Oy/C@Fe34 composites and paraffin wax were mixed at 50°C according to the mass ratio of 15 wt.%,20 wt.%and 25 wt.%,and pressed in a special mold to make coaxial rings(inner diameter=3.04 mm,outer diameter-7 mm),which were denoted as S-1,S-2 and S-3,respectively.[Results]SEM images illustrate the preparation process of iD mesoporous carbon-coated manganese oxide embedded with Fe3O4 nanoparticles composites(Mn_(x)O_(y)/C@Fe_(3)O_(4)).Most of the manganese oxide(Mn,Oy)was reduced to granular after heat treatment,while the outer carbon layer remains its 1D morphology and the carbon layer is interspersed with Fe_(3)O_(4) nanoparticles.The diffraction peaks of MnO_(2) nanowires align well with the body-centered tetragonal a-MnO2.For the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites,the signals of α-MnO_(2) disappears,followed by the emergence of Mn_(3)O_(4) and three prominent diffraction peaks for the cubic MnO.In addition,four weak diffraction peaks correspond to the magnetite Fe_(3)O_(4),consistent with the HRTEM results.The corresponding nitrogen adsorption-desorption isotherm and pore size distribution curve are presented to further analyze the mesoporous structure of composite.The surface composition and element valence states of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite were investigated by using XPS.The polarization relaxation processes were analyzed according to the Debye theory which describes the relationship between e'and e".Besides the polarization loss,the contribution of the conduction loss plays an important role for the overall dielectric loss.The magnetization curve of Mn_(x)O_(y)/C@Fe_(3)O_(4) exhibits typical ferromagnetic behavior.The permittivity parameter(Co),defined as Co=u"(u)^(-2)f^(-1) determine the contribution of eddy current effect to magnetic loss.The tand values are all larger than those of tand,for the three samples,indicating that the loss capacity of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites is mainly derived from the dielectric loss.Although tand,is smaller,it plays an important role in improving the impedance matching of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites.When the filler loading is 15 wt.%,the RL of sample S-1 is about-10.0 dB at the thickness of 1.5 mm with narrow EAB.As the filler loading increased to 20 wt.%,the RL of sample S-2 reached-62.0 dB at a thickness of 2.2 mm and the EAB was 6.4 GHz at a small thickness of 1.7 mm.When the filler loading is further increased to 25 wt.%,the microwave absorption performance of sample S3 decreased significantly with a little region of RL<-10.0 dB at the thickness of 5.0 mm.The values of[Zin/Zol of the three samples at thicknesses of 1.5-5.0 mm were calculated.Due to good impedance matching of S-2,the incident EMW can enter the material and then can be dissipated through dipole polarization loss,interface polarization loss,conduction loss,eddy current loss and natural ferromagnetic resonance loss.[Conclusions]1D Mn_(x)O_(y)/C@Fe_(3)O_(4) was synthesized via a process involving the coating of polydopamine,adsorption of Fe(ll)salts and heat treatment,using MnO_(2) nanowires as templates.The multi-component heterostructure of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite(Mn_(3)O_(4),MnO,Fe_(3)O_(4),and C)enhances the interfacial interactions between the different phases,providing increased interface polarization loss under the action of an alternating electromagnetic field.The numerous defects and terminal groups in the mesoporous carbon provide abundant dipole polarization centers.Additionally,the presence of mesopores reduces the weight of the material while increasing the multiple scattering losses of the electromagnetic waves within the material.The ID carbon structure in the matrix forms a conductive network between adjacent fibers,facilitating electron migration and transition,thereby enhancing conductive loss.The incorporation of magnetic Fe_(3)O_(4) nanoparticles introduces eddy current loss and natural ferromagnetic resonance loss,thus increasing magnetic loss.Moreover,the synergistic effect between dielectric and magnetic losses improves the impedance matching of the material,leading to excellent EMW absorption performance.展开更多
基金supported by the National Natural Science Foundation of China(52275296)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘This study aims to investigate the impact of middle ear effusion(MEE)on sound transmission in the human ear and its potential diagnostic significance.Firstly,the material properties of specific structures were adjusted based on the existing human ear finite element(FE)model,and the accuracy of the model was validated using experimental data.Secondly,six FE models were developed to simulate varying degrees of MEE by systematically altering the material properties of the middle ear cavity(MEC)at different anatomical locations.Finally,the effects of these six FE models,representing varying degrees of MEE,on sound transmission characteristics and energy absorption(EA)rate in the human ear were systematically analyzed.When the degree of MEE is less than 50%of the MEC volume,its impact on the sound transmission characteristics of the human ear remains minimal,resulting in an estimated hearing loss of approximately 3 dB,with EA rate remaining close to normal levels.Once the effusion exceeds 50%of the MEC volume,a significant deterioration in acoustic transmission is observed,accompanied by a flattening of the EA curve and a drop in EA rates to below 20%.When the effusion completely fills the MEC,the maximum hearing loss reaches 46.47 dB,and the EA rate approaches zero across the entire frequency range.These findings provide theoretical insights into the biomechanical effects of MEE on human auditory transmission and offer a reference for clinical diagnosis and evaluation.
基金Project (No. 30200266) supported by the National Natural Science Foundation of China
文摘A patented kinetic uricase method was evaluated for serum uric acid assay. Initial absorbance of the reaction mixture before uricase action （A0） was obtained by correcting the absorbance at 293 nm measured before the addition of uricase solution, and background absorbance （Ab） was predicted by an integrated method. Uric acid concentration in reaction solution was calculated from AA, the difference between A0 and Ab, using the absorptivity preset for uric acid. This kinetic uricase method exhibited CV〈4.3% and recovery of 100%. Lipids, bilirubin, hemoglobin, ascorbic acid, reduced glutathione and xanthine 〈0.32 mmol/L in serum had no significant effects. △A linearly responded to 1.2 to 37.5 μmol/L uric acid in reaction solution containing 15 μl serum. The slope of linear response was consistent with the absorptivity preset for uric acid while the intercept was consistent with that for serum alone. Uric acid concentrations in clinic sera by different uricase methods positively correlated to each other. By Bland-Altman analysis, this kinetic uricase method accorded with that by quantifying the total change of UV absorbance on the completion of uricase reaction. These results demonstrated that this kinetic uricase method is reliable for serum uric acid assay with enhanced resistance to both xanthine and other common errors, wider range of linear response and much lower cost.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51176085 and 51206086)
文摘We derive the expressions of the first and second harmonic signals on the basis of absorption spectral and lock-in theories, and determine the gas concentration according to the ratio of second and first harmonic signals. It is found that the X and Y components of the harmonic signals are influenced by the phase shift between the detection and reference signal, and the phase shift can be any value in a range from 0 to 2π, which is different from the results obtained previously. Meanwhile, an additional item caused by the residual amplitude modulation will make a great contribution to the second harmonic signal, and may not be neglected under low absorbance conditions. Theoretical analysis indicates that subtracting back-ground signal from the second harmonic signal can remove the influence of this item, and can improve the measurement accuracy of gas concentration. On this basis, we select the transition of CO2 at 6527.64 cm-1 to analyse the approximation errors during the derivation by numerical simulation and then measure the CO2 concentration under low absorbance conditions, with absorbance varying from 1‰ to 6‰.
基金funded by the National Science Fund of China (Nos. 51138006, 51290284)the National High-Tech R&D Program (863) of China (No. 2013AA065205)+1 种基金the Key Science and Technology Project of Shenzhen Water AuthorityThe Collaborative Innovation Center for Regional Environmental Quality also supported this research
文摘Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading pollutants during storage, and its effect on dissolved organic matter（DOM） was investigated in this study. Solar light significantly decreased the UV_（254） absorbance and fluorescence（FLU） intensity of reclaimed water.However, its effect on the dissolved organic carbon（DOC） value of reclaimed water was very limited. The decrease in the UV_（254） absorbance intensity and FLU excitation–emission matrix regional integration volume（FLU volume） of reclaimed water during solar light irradiation was fit with pseudo-first order reaction kinetics. The decrease of UV_（254） absorbance was much slower than that of the FLU volume. Ultraviolet light in solar light had a key role in decreasing the UV_（254） absorbance and FLU intensity during solar light irradiation. The light fluence-based removal kinetic constants of the UV_（254） and FLU intensity were independent of light intensity. The peaks of the UV_（254） absorbance and FLU intensity with an apparent molecular weight（AMW） of 100 Da to 2000 Da decreased after solar irradiation, whereas the DOC value of the major peaks did not significantly change.
文摘Near-infrared (NIR) spectroscopy was applied to reagent-free quantitative analysis of polysaccharide of a brand product of proprietary Chinese medicine (PCM) oral solution samples. A novel method, called absorbance upper optimization partial least squares (AUO-PLS), was proposed and successfully applied to the wavelength selection. Based on varied partitioning of the calibration and prediction sample sets, the parameter optimization was performed to achieve stability. On the basis of the AUO-PLS method, the selected upper bound of appropriate absorbance was 1.53 and the corresponding wavebands combination was 400 - 1880 & 2088 - 2346 nm. With the use of random validation samples excluded from the modeling process, the root-mean-square error and correlation coefficient of prediction for polysaccharide were 27.09 mg·L<sup>-</sup><sup>1</sup> and 0.888, respectively. The results indicate that the NIR prediction values are close to those of the measured values. NIR spectroscopy combined with AUO-PLS method provided a promising tool for quantification of the polysaccharide for PCM oral solution and this technique is rapid and simple when compared with conventional methods.
文摘In the article titled“A rapid absorbance-based growth assay to screen the toxicity of oligomer Aβ42 and protect against cell death in yeast”,published on pages 1931–1936,Issue 10,Volume 15 of Neural Regeneration Research(Bharadwaj and Martins,2020),there is an error in the title.It should read:A rapid absorbance-based growth assay to screen the toxicity of oligomer Aβ42 and protection against cell death in yeast.
文摘Five phospholipids in human placenta were determined by phosphorus 31 nuclear magnetic resonance(^(31)P NMR)spectroscopy and thin-layer chromatography(TLC) scanning combined with the corrective method of absorbance proportional coefficient. The NMR spectrometer used this investigation was a Bruker AM-500 spectrometer operating at 202.4 MHz for ^(31)P chemical shifts are relative to 85% phosphoric acid. TIC was carried out by silica gel H plate developed in chloroform-methanol-glacial acetic acid-ethanol-water(25:4:6:2:0.5),with Vaskovsky reagent as colour -developing agent of phospholipids.
文摘Objective： To investigate the correlation of fibrinogen level and absorbance change in both PT and APTT clotting curves on BCSXP Analyzer. Methods：A serial of standard fibrinogen and 250 patient plasma samples with different qualities（normal, hemolysis, icterus, and lipemia） were run on BCSXP for assays PT, APTT and Fibrinogen. The absorbance change（DeltaA） from baseline to plateau in clotting curve was retrieved and analyzed on its correlation with the Fibrinogen result. Influence of plasma quality and PT/ APTT result on this correlation was also studied respectively. Results：Both PT-DeltaA and APTT-DeltaA showed good linear regres- sion with fibrinogen level in the sample, with R2 close to 0.90 in both standard and patient samples. Hemolysis（H）, itcterus（I） and lipemia（L） of the sample with valid clotting curves were found to have no significant difference in this correlation from normal（N） sample（R2： 0.83H, 0.92I, 0.81L and 0.79N in PT; 0.89H, 0.95l, 0.91L and 0.89N in APTT） in either PT or APTT curve. PT or APTT result also has little impact on this correlation（0.71 in range 7 - 10 sec, 0.56 inl0 - 20 sec, and 0.70 in 20 sec-; R2 in APTT： 0.88 in 20-30 sec, 0.92 in 30-40 sec, and 0.95 in 40 sec-）. Conclusion：The absorbance change in either PT or APTT clotting curve correlates well with the fibrinogen level in plasma, which is independent of plasma quality PT or APTT results. The absorbance change can be used as an alternative way to roughly estimate fibrinogen level in either PT or APTT clotting curve when the result of clauss-based fibrinogen measurement is not available.
文摘The optical absorbance in near UV wavelength region in SnO 2 nanoclusters in an external electric field is determined at room temperature. The absorbance spectra as applied field and the absorbance variations with the applied field are obtained.The relation between absorbance change and applied field is non-linear, and is saturated at high field region.
文摘In the twenty first century research works, there may be a need to achieve a more reliable research result through a synergy between engineers and biological researchers. The peak absorbance data for various interacting systems were measured. These were used to show that the antiretroviral drug has the effect of increasing the peak absorbance values of both the uninfected and infected blood components, i.e., the drugs are made able to increase the light absorption capacity of the blood cells. For drug 2 that contains three components including Efavirenz, the drug effect on lymphocytes was increased by about 38% for patients that had been on antiretroviral drug treatment. Mathematical models were proposed and used in determining the coating effectiveness of antiretroviral drugs in the presence and absence of HIV. The use of the findings of this work by pharmaceutical industries may help in the search for more effective antiretroviral drugs for the treatment of HIV patients.
文摘Metalorganic chemical vapour deposition (MOCVD) method was used to deposit zinc oxide thin films on soda-lime glass substrates at temperatures of 330°C, 360°C, 390°C and 420°C, using zinc acetate as the precursor. Compressed air was used as the carrier gas at a flow rate of 2.5 dm3 per minute. Each deposition was carried out for two hours under atmospheric pressure. FTIR measurements were subsequently made on the produced thin films to determine their struc ture and trend with deposition temperatures. The measurements showed the presence of lingering functional groups of organic, oxide and nitride origin, which prominently moderated the natural vibrational modes of the material within their respective affiliate wavenumbers, as well as three slight but evident trends in absorbance peaks, cut-off wave length, and the existence of the functional groups with temperature. The produced materials are expected to be useful for enhanced solar cells, triggering sensor devices, p-doped zinc oxide, etc.
文摘In this work, we present the growth and optical characterization of carbon nanotube/TiO2 anatase nanocomposites. The composites are obtained by doping a bulk of anatase nanometric grains with different weight percentages of carbon nanotube (from 0.1% to 50%). We observe that only for tube concentrations between 0.1% and 2%, the growth process shows the formation of a matrix where carbon nanotubes are uniformed and dispersed in a bulk of TiO2 grains. Moreover, the X-ray photoelectron spectroscopy and surface morphology analysis (conducted from AFM images) indicated that the CNT absorption is a simple physisorption without chemical bonds formations between tube and dioxide. Finally, absorption in all the visible range has the increase of about 60% at very low concentration (2%) of carbon nanotubes.
基金supported by the National Nature Science Foundation of China(Nos.22305066 and 52372041).
文摘High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorp-tion(EMWA)performance at elevated temperatures,which severely restricts their practical application.In this study,we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide(RGO)/epoxy resin(EP)metacomposites that integrate both electromagnetic parameters and metamaterial design concepts.Due to the discrete distribution of the units,electromagnetic waves can more easily penetrate the interior of materials,thereby exhibiting stable microwave absorption(MA)performance and impedance-matching characteristics suitable across a wide temperature range.Consequently,exceptional MA properties can be achieved within the tem-perature range from 298 to 473 K.Furthermore,by carefully controlling the structural parameters in RGO metacomposites,both the resonant frequency and effective absorption bandwidth(EAB)can be optimized based on precise manipulation of equivalent electromagnetic parameters.This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.
基金supported by the Guangdong Basic and Applied Basic Research Foundation (No.2023A1515010093)the Shenzhen Fundamental Research Program (Stable Support Plan Program)(Nos.JCYJ20220809170611004, 20231121110828001 and 20231121113641002)the National Taipei University of Technology-Shenzhen University Joint Research Program (No.2024001)。
文摘In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.
基金supported by the National Nat-ural Science Foundation of China(Nos.51872238,52074227,and 21806129)the Fundamental Research Funds for the Central Universities,China(Nos.3102018zy045 and 3102019AX11)+2 种基金the Guangdong Basic and Applied Basic Research Foundation,China(No.2024A1515010298)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2017JQ5116 and 2020JM-118)the Key Laboratory of Icing and Anti/De-icing of CARDC(No.IADL20220401).
文摘Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood.In this study,we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride(ChCl)and ethylene glycol(EG).Owing to the unique properties of deep eutectic gels,the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded.Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG,with HB-induced conductive loss following similar pat-terns.At a ChCl and EG molar ratio of 2.4,the gel labeled G22-CE2.4 exhibited the best EMW absorption performance,characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm.This superior performance is attributed to the synergistic ef-fects of excellent conductive loss and impedance matching generated by the optimal number of HB.This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.
基金supported by the National Natural Science Foundation of China(No.52377026)Taishan Scholars and Young Experts Program of Shandong Province,China(No.tsqn202103057)the Natural Science Foundation of Shandong Province,China(No.ZR2024ME046).
文摘With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance electromagnetic wave(EMW)ab-sorbers is an effective method to solve the above issue and has attracted the attention of many researchers.As a typical magnetic material,ferrite plays an important role in the design of high-performance EMW absorbers,and related research focuses on diversified synthesis methods,strong absorption performance,and refined microstructure development.Herein,we focus on the synthesis of ferrites and their composites and introduce recent advances in the high-temperature solid-phase method,sol-gel method,chemical coprecipitation method,and solvent thermal method in the preparation of high-performance EMW absorbers.This review aims to help researchers understand the advantages and disadvantages of ferrite-based EMW absorbers fabricated through these methods.It also provides important guidance and reference for researchers to design high-performance EMW absorption materials based on ferrite.
基金support of the Key Science Research Project in Colleges and Universities of Anhui Province,China(No.2022AH050813)the Medical Special Cultivation Project of Anhui University of Science and Technology,China(No.YZ2023H2A002).
文摘Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In this study,a flake-like nickel cobaltate/re-duced graphene oxide/melamine-derived carbon foam(FNC/RGO/MDCF)was successfully fabricated through a combination of solvo-thermal treatment and high-temperature pyrolysis.Results indicated that RGO was evenly distributed in the MDCF skeleton,providing ef-fective support for the load growth of FNC on its surface.Sample S3,the FNC/RGO/MDCF composite prepared by solvothermal method for 16 h,exhibited a minimum reflection loss(RL_(min))of-66.44 dB at a thickness of 2.29 mm.When the thickness was reduced to 1.50 mm,the optimal effective absorption bandwidth was 3.84 GHz.Analysis of the absorption mechanism of FNC/RGO/MDCF revealed that its excellent absorption performance was primarily attributed to the combined effects of conduction loss,multiple reflection,scattering,in-terface polarization,and dipole polarization.
基金supported by the Science and Technology Department of Qinghai Province,China(No.2022-ZJ-932Q).
文摘The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.This study satisfactorily fabricated a series of MoS_(2)/BN-xyz composites(which were characterized by the weight ratio of MoS_(2)to BN,denoted by xy:z)through chemical vapor depos-ition,which resulted in their improved thermal stability and thermal transmission performance.The results show that the remaining mass of MoS_(2)/BN-101 was as high as 69.25wt%at 800℃under air atmosphere,and a temperature difference of 31.7℃was maintained between the surface temperature and the heating source at a heating temperature of 200℃.Furthermore,MoS_(2)/BN-301 exhibited an im-pressive minimum reflection loss value of-32.21 dB at 4.0 mm and a wide effective attenuation bandwidth ranging from 9.32 to 18.00 GHz(8.68 GHz).Therefore,these simplified synthesized MoS_(2)/BN-xyz composites demonstrate great potential as highly efficient con-tenders for the enhancement of microwave absorption performance and thermal conductance.
基金financially supported by the National Natural Science Foundation of China (52462032, 62274018, 52462031)Natural Science Foundation of Yunnan Province (202501AT070353, 202101BE070001-049)+2 种基金the Xinjiang Construction Corps Key Areas of Science and Technology Research Project (2023AB029)the Tianchi Talent Program of Xinjiang Uygur Autonomous Region (2024, Jiangzhao Chen)the Key Project of Chongqing Overseas Students Returning to China Entrepreneurship and Innovation Support Plan (cx2023006)。
文摘In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-cation perovskites(MCPs) have been extensively used as absorber thin films in perovskite solar cells(PSCs), achieving high power conversion efficiencies(PCE) over 26%^([1, 2]).
基金National Natural Science Foundation of China (52371171, 52222106, 51971008, 52121001)Fund of National Key Laboratory of Scattering and Radiation (Beijing Institute of Environmental Features)。
文摘[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broadband absorbers remains a challenge in terms of practical applications.EMW absorbing materials primarily rely on the magnetic loss of magnetic materials and/or the dielectric loss of dielectric materials to convert EMW energy into thermal energy for dissipation.Among various magnetic materials,Fe_(3)O_(4) plays an irreplaceable role in EMW absorption due to its high saturation magnetization,low cost and compatible dielectric loss in the gigahertz frequency range.Nevertheless,the high density,large matching thickness and narrow absorption bandwidth of Fe_(3)O_(4) pose significant challenges for practical applications.In contrast,one-dimensional(1D)structures not only retain the characteristic properties of lightweight,chemical stability and high dielectric loss,but also exhibit anisotropic structures and large aspect ratios.Additionally,researchers have found that the minimum reflection loss(RL)of hollow carbon materials with mesopores is nearly four times that of non-porous hollow carbon materials and nine times that of dense carbon materials.According to Maxwell's EMW theory,composites consisting of Fe_(3)O_(4) and one-dimensional(1D)mesoporous carbon materials can leverage their respective advantages by optimizing the composition and structure of the composites to balance u,and Er,thereby enhancing EMW absorption performance.Additionally,numerous studies have demonstrated that composites composed of multi-component heterostructures significantly enhance the EAB.This enhancement is primarily ascribed to the numerous interface polarization losses generated by the additional heterostructure interfaces,which also improve the overall impedance matching of the composites.In this study,we leverage the advantages of magnetic/carbon composites,one-dimensional(1D)mesoporous carbon and multi-component heterostructures to prepare a composite of 1D mesoporous carbon-coated manganese oxide(Mn_(3)O_(4) and MnO,denoted as Mn_(x)O_(y))embedded with Fe_(3)0_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4)).This composite was synthesized and its formation mechanism and microstructure were analyzed in detail.At the same time,the influence of this Mn_(x)O_(y)/C@Fe_(3)O_(4) structure on EMW properties and absorbing performance was further discussed.[Methods]Firstly,MnO_(2) nanowires were synthesized by using a simple hydrothermal method.Then,the MnO_(2) nanowires served as templates for the synthesis of MnO_(2)/PDA@Fe^(3+)composites through the in-situ polymerization of dopamine and Fe^(3+)adsorption.Finally,1D mesoporous carbon-coated manganese oxide composite embedded with Fe_(3)O_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4))composites were obtained after heat treatment at 550℃ in N_(2).The crystal structure of the samples was analyzed using X-ray diffractometer with Cu Ka irradiation.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(TEM)were used to observe microstructure and morphology of the samples.Nitrogen sorption measurements were obtained at 77 K on a Quantachrome surface area and pore size analyzer to measure the specific surface area and pore size distribution.XPS analysis was performed on X-ray photoelectron spectrometer with monochromatic Al Ka radiation.Magnetization curves of the samples were recorded with a Quantum Design physical property measurement system(PPMS-9)at room temperature.The electromagnetic parameters of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites were measured using an Agilent N5230C network analyzer in the frequency range of 2-18 GHz.For electromagentic testing,the Mn,Oy/C@Fe34 composites and paraffin wax were mixed at 50°C according to the mass ratio of 15 wt.%,20 wt.%and 25 wt.%,and pressed in a special mold to make coaxial rings(inner diameter=3.04 mm,outer diameter-7 mm),which were denoted as S-1,S-2 and S-3,respectively.[Results]SEM images illustrate the preparation process of iD mesoporous carbon-coated manganese oxide embedded with Fe3O4 nanoparticles composites(Mn_(x)O_(y)/C@Fe_(3)O_(4)).Most of the manganese oxide(Mn,Oy)was reduced to granular after heat treatment,while the outer carbon layer remains its 1D morphology and the carbon layer is interspersed with Fe_(3)O_(4) nanoparticles.The diffraction peaks of MnO_(2) nanowires align well with the body-centered tetragonal a-MnO2.For the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites,the signals of α-MnO_(2) disappears,followed by the emergence of Mn_(3)O_(4) and three prominent diffraction peaks for the cubic MnO.In addition,four weak diffraction peaks correspond to the magnetite Fe_(3)O_(4),consistent with the HRTEM results.The corresponding nitrogen adsorption-desorption isotherm and pore size distribution curve are presented to further analyze the mesoporous structure of composite.The surface composition and element valence states of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite were investigated by using XPS.The polarization relaxation processes were analyzed according to the Debye theory which describes the relationship between e'and e".Besides the polarization loss,the contribution of the conduction loss plays an important role for the overall dielectric loss.The magnetization curve of Mn_(x)O_(y)/C@Fe_(3)O_(4) exhibits typical ferromagnetic behavior.The permittivity parameter(Co),defined as Co=u"(u)^(-2)f^(-1) determine the contribution of eddy current effect to magnetic loss.The tand values are all larger than those of tand,for the three samples,indicating that the loss capacity of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites is mainly derived from the dielectric loss.Although tand,is smaller,it plays an important role in improving the impedance matching of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites.When the filler loading is 15 wt.%,the RL of sample S-1 is about-10.0 dB at the thickness of 1.5 mm with narrow EAB.As the filler loading increased to 20 wt.%,the RL of sample S-2 reached-62.0 dB at a thickness of 2.2 mm and the EAB was 6.4 GHz at a small thickness of 1.7 mm.When the filler loading is further increased to 25 wt.%,the microwave absorption performance of sample S3 decreased significantly with a little region of RL<-10.0 dB at the thickness of 5.0 mm.The values of[Zin/Zol of the three samples at thicknesses of 1.5-5.0 mm were calculated.Due to good impedance matching of S-2,the incident EMW can enter the material and then can be dissipated through dipole polarization loss,interface polarization loss,conduction loss,eddy current loss and natural ferromagnetic resonance loss.[Conclusions]1D Mn_(x)O_(y)/C@Fe_(3)O_(4) was synthesized via a process involving the coating of polydopamine,adsorption of Fe(ll)salts and heat treatment,using MnO_(2) nanowires as templates.The multi-component heterostructure of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite(Mn_(3)O_(4),MnO,Fe_(3)O_(4),and C)enhances the interfacial interactions between the different phases,providing increased interface polarization loss under the action of an alternating electromagnetic field.The numerous defects and terminal groups in the mesoporous carbon provide abundant dipole polarization centers.Additionally,the presence of mesopores reduces the weight of the material while increasing the multiple scattering losses of the electromagnetic waves within the material.The ID carbon structure in the matrix forms a conductive network between adjacent fibers,facilitating electron migration and transition,thereby enhancing conductive loss.The incorporation of magnetic Fe_(3)O_(4) nanoparticles introduces eddy current loss and natural ferromagnetic resonance loss,thus increasing magnetic loss.Moreover,the synergistic effect between dielectric and magnetic losses improves the impedance matching of the material,leading to excellent EMW absorption performance.
