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1.
Front Nutr ; 11: 1419379, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-39206314

RESUMEN

Aim: The study aimed to investigate the link between dietary copper, iron, zinc, selenium intake with osteopenia and osteoporosis in elderly hypertensive patients. Methods: The data of hypertensive patients were extracted from the National Health and Nutrition Examination Survey 2005-2010, 2013-2014, and 2017-2018. Data of dietary iron, zinc, copper and selenium intakes were obtained according to 24-h diet recall interviews. Osteopenia and osteoporosis were determined based on the bone mineral density. Weighted liner regression and weighted logistic regression were employed to assess the association between iron, zinc, copper, and selenium intakes with osteopenia and osteoporosis. All results were presented as ß, odds ratios (ORs), and 95% confidence intervals (CIs). Results: In total, 5,286 elderly hypertensive patients were included. Among them, 2,961 (56.02%) patients have osteopenia, and 566 (10.71%) have osteoporosis. After adjusting all covariates, dietary copper intake ≥the recommended daily allowance was positively correlated with bone mineral density on total femur (ß = 0.086, 95% CI: 0.021-0.152) and femoral neck (ß = 0.097, 95% CI: 0.016-0.178). Dietary zinc intake ≥the recommended daily allowance was also positively correlated with bone mineral density on total femur (ß = 0.092, 95% CI: 0.030-0.153) and femoral neck (ß = 0.122, 95% CI: 0.050-0.193). Dietary copper (O = 0.581, 95% CI: 0.394-0.858) and zinc (OR = 0.595, 95% CI: 0.429-0.827) intake ≥the recommended daily allowance levels were related to increased odds of osteoporosis in elderly with hypertension. Conclusion: Higher dietary copper and zinc intake was associated with lower odds of osteoporosis in the elderly hypertensive patients. Higher dietary intake included copper and zinc may be beneficial for the bone health in the elderly hypertensive patients.

2.
ACS Appl Mater Interfaces ; 16(27): 35716-35722, 2024 Jul 10.
Artículo en Inglés | MEDLINE | ID: mdl-38917377

RESUMEN

Low detectability and camouflage skills in the electromagnetic wave and light frequency range provide survival advantages for natural creatures and are essential for understanding the operational principles of the biosphere. Taking inspiration from natural mutualistic symbiosis, this paper proposes a symbiotic electromagnetic shadow camouflage mechanism based on a superdispersive surface, aiming to investigate its impact on the observability of specific objects. The design and experimental results indicate that the symbiotic shadow dihedral can significantly reduce overall scattering quantity, which reaches at least 10 dB shrink in the 12-18 GHz frequency range compared to the contrast object. Unlike known camouflage methods, the electromagnetic shadow technology shrinks the overall scattering without any coating and shield metal target while probably offering extensive functional design freedom for the concealed object, creature, or equipment. This also provides a hint to explore symbiosis-related camouflage phenomena in nature.

3.
Adv Sci (Weinh) ; 11(4): e2306119, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-38036422

RESUMEN

Tunable radar stealth structures are critical components for future military equipment because of their potential to further enhance the design space and performance. Some previous investigations have utilized simple origami structures as the basic adjusting components but failed to achieve the desired broadband microwave absorbing characteristic. Herein, a novel double-broadband switchable microwave absorbing grid structure has been developed with the actuators of inflatable Kresling origami structures. Geometric constraints are derived to endow a bistable feature with this origami configuration, and the stable states are switched by adjusting the internal pressure. An ultra-broadband microwave absorbing structure is proposed with a couple of complementary microwave stealth bands, and optimized by a particle swarm optimization algorithm. The superior electromagnetic performance results from the mode switch activating different absorbing components at corresponding frequencies. A digital adjusting strategy is applied, which effectively achieves a continuously adjusting effect. Further investigations show that the proposed structure possesses superior robustness. In addition, minimal interactions are found between adjacent grid units, and the electromagnetic performance is mainly related to the duty ratio of the units in different states. They have enhanced the microwave absorbing performance of grid structures through a tunable design, a provided a feasible paradigm for other tunable absorbers.

4.
Bioengineered ; 13(4): 8174-8186, 2022 04.
Artículo en Inglés | MEDLINE | ID: mdl-34738872

RESUMEN

Osteosarcoma (OS) is the most common high-grade malignant bone tumor in teenagers. MicroRNAs can function as posttranscriptional regulators of gene expression, playing critical roles in cancer dev-877-3p in OS. Quantitative real-time RT-PCR was carried out for detecting miR-877-3p expression in OS. The effects of miR-877-3p on proliferation was analyzed via MTT, colony formation, and flow cytometry assays. Angiogenesis of endothelial cells were investigated by wound healing and tube formation assay. Gene profiling based on PCR array and luciferase reporter assay were conducted to determine target genes of miR-877-3p. In-vivo study was used to determine the effects of miR-877-3p on the tumor growth. The expression of miR-877-3p was markedly downregulated in OS tissues and cell lines. Low expression of miR-877-3p predicts poor prognosis of OS patients. miR-877-3p overexpression was found to inhibit the proliferation of OS cell lines. The angiogenesis assays showed that miR-877-3p attenuated the angiogenesis. Further mechanism studies showed that miR-877-3p can reduce (Fibroblast Growth Factor 2) FGF2 expression in OS cells by binding to the 3'UTR end of FGF2. Moreover, increased expression of miR-877-3p was responsible for the inhibition of tumor growth and angiogenesis. Taken together, our findings indicated that miR-877-3p might exhibit tumor suppressive role by targeting FGF2 signaling, which may serve as potential target for OS.


Asunto(s)
Neoplasias Óseas , MicroARNs , Osteosarcoma , Adolescente , Neoplasias Óseas/metabolismo , Línea Celular Tumoral , Movimiento Celular , Proliferación Celular/genética , Células Endoteliales/metabolismo , Factor 2 de Crecimiento de Fibroblastos/genética , Humanos , MicroARNs/genética , MicroARNs/metabolismo , Osteosarcoma/metabolismo
5.
Transl Neurosci ; 12(1): 138-144, 2021 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-33976931

RESUMEN

OBJECTIVE: Our previous in vivo study found that resveratrol (Res), which is a phytoalexin, attenuated 6-hydroxydopamine (6-OHDA)-induced motor dysfunction by activating the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway in rats. Therefore, we further explored the protective effect of Res on 6-OHDA-induced damage to PC12 cells in vitro with respect to the PI3K/Akt signaling pathway. METHODS: We incubated PC12 cells with 75 µM 6-OHDA for 24 h, and Res was then added at a final concentration of 25 µM; the protective effect was examined via MTT and lactate dehydrogenase (LDH) assays. In addition, the PI3K inhibitor LY294002 was used to investigate the potential mechanism. JC-1 staining was used to detect the mitochondrial membrane potential (MMP), and western blotting (WB) was used to detect the phosphorylation of Akt-Ser473. RESULTS: Compared with that in the control, the cell viability, total superoxide dismutase (SOD) activity, MMP, and p-Akt-Ser473 level of 6-OHDA-treated PC12 cells were significantly decreased, while the leakage rate of LDH was increased. And after treatment with 25 µM Res, the cell viability, total SOD activity, MMP, and p-Akt-Ser473 level of 6-OHDA-treated PC12 cells were significantly increased compared with those of the control cells, while the leakage rate of LDH was decreased. These effects of Res were antagonized by LY294002. CONCLUSIONS: Res ameliorates 6-OHDA-induced damage to PC12 cells via activation of the PI3K/Akt signaling pathway.

6.
Injury ; 51(6): 1362-1366, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32291087

RESUMEN

PURPOSE: This study was to retrospectively evaluate clinical outcomes of geriatric patients with patella fracture treated by percutaneous cerclage wiring and to introduce the surgical technique. METHODS: From January 2009 to December 2015, fifty-seven consecutive geriatric patients of type 34-C patellar fracture underwent closed reduction and percutaneous cerclage wiring fixation in our hospital. Visual Analog Scale (VAS) score, Levack score system, WOMAC test form of pain, stiffness and function, and knee joint range of motion (ROM) were applied for functional evaluation. RESULTS: Fifty-three patients were followed up for a mean period of 36 months (12 to 82 months). All fractures were unioned, no wound infection, second displacement of fracture fragment or wire migration was found. Wire breakage happened in one case at six months post-operation. Thirteen patients had hardware removed, nine cases for implant irritation at the knot and four cases for no specific reason. No patient developed postoperative knee stiffness, and range of motion was 128.6° (110-140). The average VAS score of emotional knee function was 87.5 (65-99) preinjury and 78.1 (53-95) at the last follow-up. 86.8% (46/53) patients considered that they regained more than 80% of their knee function. The average Levack score was 10.0 (6-12), which included thirty-five evaluations of "excellent" and eighteen of "good". The average WOMAC score was 21.3 (13-37). CONCLUSIONS: Percutaneous cerclage wiring fixation is a viable option for type 34-C patella fracture in geriatric patients.


Asunto(s)
Hilos Ortopédicos , Fijación Interna de Fracturas , Fracturas Óseas/cirugía , Rótula/lesiones , Anciano , Anciano de 80 o más Años , Tornillos Óseos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Radiografía , Rango del Movimiento Articular , Estudios Retrospectivos , Resultado del Tratamiento , Escala Visual Analógica
7.
Adv Sci (Weinh) ; 7(2): 1902162, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31993290

RESUMEN

Smart structures with manipulatable properties are highly demanded in many fields. However, there is a critical challenge in the pursuit of transparent windows that allow optical waves (wavelength of µm-nm) for transmitting while blocking microwave (wavelength of cm) in terms of absorbing electromagnetic energy, specifically for meeting the frequency requirement for the 5th generation (5G) mobile networks. For fundamentally establishing novel manipulatable microwave absorbing structures, here, new polymeric aqueous gels as both optically transparent materials and microwave absorbing materials are demonstrated, in which polar networks play significant roles in attenuating electromagnetic energy. By manipulating the hydrogen bonding networks, the resulting optically transparent solid-state gels are able to offer the capabilities for absorbing microwaves. Interestingly, such gels can be switched into an optically opaque state via converting the amorphous state into a polycrystal state when the temperature is decreased. Such ionic conductive gels can endow the assembled sandwich windows with effective microwave absorbing capability in the range of 15-40 GHz, covering a branch of 5G frequency bands. The results highlight a new strategy for using ionic conductive gels to design and fabricate manipulatable microwave stealth structures for various applications.

8.
J Acoust Soc Am ; 146(1): 166, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-31370652

RESUMEN

Acoustic metasurfaces show non-traditional abilities in wave manipulation and provide alternate mechanisms for information communication and invisibility technology. However, most of the mechanisms remain narrow band (relative bandwidth ∼5%), and a wideband trait is essential for engineering applications. For example, controllable effective material properties-reflection or transmission phase-has barely been realized in wideband because the intrinsic dispersion relation is not always editable. In this paper, wideband reflection phase editing is realized, and wideband invisibility of a phase preserved Huygens's metasurface on a flat background is achieved with anomalous reflection. This metasurface is built with proposed unsymmetrical twin Helmholtz resonators which reach a predefined dispersion relation target value. The total instantaneous acoustic fields show nearly identical carpeting effects in a consecutive band with relative bandwidth 52.1% (from 5400 to 9200 Hz) in simulation and experiment.

9.
Exp Gerontol ; 124: 110653, 2019 09.
Artículo en Inglés | MEDLINE | ID: mdl-31295526

RESUMEN

This study aimed to determine whether resveratrol (Res) delays the progression of 6-hydroxydopamine (6-OHDA)-induced apoptosis via activating the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway. Sprague-Dawley (SD) rats were unilaterally injected with 6-OHDA (8 µg/4 µL) into the substantia nigra of the midbrain. Res (15 and 30 mg/kg) was given orally to the rats for a total of 36 days to examine its protective effects. We first tested whether Res can delay the progression of 6-OHDA-induced damage by measuring weight and performance on behavioral tests (rotarod, open field test and grid test) and further explored whether this effect is related to the activation of the PI3K/Akt signaling pathway using immunohistochemistry (IHC) and Western blotting (WB). Our results showed that the damage induced by 6-OHDA gradually worsened, while Res 30 mg/kg treatment significantly improved motor function and increased body weight. Compared with those in the model group, the number of dopaminergic neurons cells and the expression of PI3K-110α, p-Akt Ser473, and pro-caspase-3 in the Res 30 mg/kg group were significantly increased, and the Bax/Bcl-2 ratio and the level of activated caspase-3 was decreased. The results indicate that Res ameliorates 6-OHDA-induced apoptosis and motor dysfunction via activating the PI3K/Akt signaling pathway, delaying the progression of Parkinson's disease (PD) symptoms in this model.


Asunto(s)
Apoptosis/efectos de los fármacos , Fármacos Neuroprotectores/farmacología , Enfermedad de Parkinson/tratamiento farmacológico , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Resveratrol/farmacología , Animales , Modelos Animales de Enfermedad , Neuronas Dopaminérgicas/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Regulación de la Expresión Génica/efectos de los fármacos , Masculino , Oxidopamina/toxicidad , Enfermedad de Parkinson/fisiopatología , Ratas , Ratas Sprague-Dawley , Transducción de Señal/efectos de los fármacos , Sustancia Negra/efectos de los fármacos , Sustancia Negra/metabolismo , Sustancia Negra/patología
10.
ACS Appl Mater Interfaces ; 11(25): 22768-22776, 2019 Jun 26.
Artículo en Inglés | MEDLINE | ID: mdl-31140776

RESUMEN

Two-dimensional lattice structures with specific geometric features have been reported to have a negative Poisson's ratio, termed as auxetic metamaterials, that is, stretching-induced expansion in the transversal direction. In this paper, we designed a novel auxetic metamaterial; by utilizing the shape memory effect of the constituent materials, the in-plane moduli and Poisson's ratios can be continuously tailored. During deformation, the curved meshes ensure the rotation of the mesh joints to achieve auxetics. The rotations of these mesh joints are governed by the mesh curvature, which continuously changes during deformation. Because of the shape memory effect, the mesh curvature after printing can be programmed, which can be used to tune the rotation of the mesh joints and the mechanical properties of auxetic metamaterial structures, including Poisson's ratios, moduli, and fracture strains. Using the finite element method, the deformation of these auxetic meshes was analyzed. Finally, we designed and fabricated gradient/digital patterns and cylindrical shells and used the auxetics and shape memory effects to reshape the printed structures.

11.
Biomed Pharmacother ; 114: 108789, 2019 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-30925459

RESUMEN

Over the past 200 years, Parkinson's disease (PD) has remained an insurmountable challenge. Despite the existence of numerous therapeutic drugs, there are still not enough treatments in the face of the complex pathogenesis of PD. Therefore, the search for more effective therapeutic drugs for PD has extremely important practical significance. Procyanidin (PC), widely found in plants such as grapes, is a bioflavonoid antioxidant with a special molecular structure that can effectively remove free radicals in the human body. To explore its possible mechanism in PD, we used 6-hydroxydopamine (6-OHDA, 8 µg) to mimic dopaminergic (DA) neuronal damage and validated this model in vivo and in vitro. in vivo, we detected an effect of PC (60 mg/kg) on the behavioural changes exhibited in 6-OHDA model rats, the number of DA neurons and the phosphorylation of protein kinase B (Akt). in vitro, we detected changes in cell viability, mitochondrial membrane potential (MMP) and total superoxide dismutase (SOD) and explored the role of PC (50 µM) by inhibiting the phosphoinositide 3-kinase (PI3K)/Akt signalling pathway with LY294002 (20 µM). The present study demonstrates that PC plays a protective role against 6-OHDA-induced neurotoxicity, which may be mediated through the activation of the PI3K/Akt signalling pathway. This study indicates a potential use for PC in the treatment and prevention of PD.


Asunto(s)
Biflavonoides/farmacología , Catequina/farmacología , Neuronas Dopaminérgicas/efectos de los fármacos , Fármacos Neuroprotectores/farmacología , Oxidopamina/farmacología , Fosfatidilinositol 3-Quinasas/metabolismo , Proantocianidinas/farmacología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Transducción de Señal/efectos de los fármacos , Animales , Supervivencia Celular/efectos de los fármacos , Neuronas Dopaminérgicas/metabolismo , Masculino , Potencial de la Membrana Mitocondrial/efectos de los fármacos , Fosforilación/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Superóxido Dismutasa/metabolismo
12.
ACS Appl Mater Interfaces ; 10(47): 40815-40823, 2018 Nov 28.
Artículo en Inglés | MEDLINE | ID: mdl-30384586

RESUMEN

Smart materials and structures with tunable electromagnetic (EM) properties are highly demanded for active environmental sensitive systems. As polar molecules in the environment, in this work, water and ice are utilized as wetting and freezing conditions to manipulate the electromagnetic response behaviors in a graphene-based composite material, aiming to achieve a smart weather-manipulated EM metamaterial. Owing to the introduced polar water and ice phase in the self-assembled porous electromagnetic attenuating networks, energy consumption of EM waves is significantly altered via multiple scattering of polar induced interfaces. In frozen conditions, a wide absorption band (2-18 GHz) with efficient absorption (reflection loss < -10 dB) has been obtained. Additionally, the mechanical feature of the as-assembled metamaterials could also be manipulated via altering the weather conditions in terms of changing the phase of the introduced water. Interestingly, the mechanical properties could be massively changed while the broadband absorption capability has rarely been impacted. Implication of the results highlights an efficient method for fabricating smart EM metamaterials that are capable of being manipulated by the environment.

13.
ACS Appl Mater Interfaces ; 10(51): 44731-44740, 2018 Dec 26.
Artículo en Inglés | MEDLINE | ID: mdl-30462493

RESUMEN

The implementation of thin structure for broadband microwave absorption is challenging due to the requirement of impedance match across several frequency bands and poor mechanical properties. Herein, we demonstrate a carbon fiber (CF) reinforced flexible thin hierarchical metastructure (HM) composed of lossy materials including carbonyl iron (CI), multiwall carbon nanotube (MWCNT), and silicone rubber (SR) with thickness of 5 mm and optimal concentration selected from 12 formulas. Optimization for the periodical unit size is applied, and impacts of structural sizes on absorption performance are also investigated. An effective process combining the vacuum bag method and the hand lay-up technique is used to fabricate the HM. Experimental reflectivity of the absorber achieves broadband absorption below -10 dB in 2-4 GHz and 8-40 GHz. The full band in 2-40 GHz is covered below -8 dB. Yielding stress of the HM is increased to 24 MPa with attachment of CF, while the fracture strain of the composite reaches 550%. The soft HM is suitable to adhere to the curved surface of objects needed to be protected from microwave radiation detection and electromagnetic interference. Enhanced mechanical properties make it possible for further practical applications under harsh service environments such as the ocean and machines with constant vibration.

14.
ACS Appl Mater Interfaces ; 10(44): 38404-38409, 2018 Nov 07.
Artículo en Inglés | MEDLINE | ID: mdl-30212180

RESUMEN

An ultrabroadband all-dielectric planar Luneburg lens has been designed and fabricated in this study, which is in the form of a radial gradient lightweight honeycomb column. Because of the novel design of a radial symmetric honeycomb-like microstructure in the subwavelength dimension and the radial gradient configuration according to the refractive index distribution of Luneburg lens, the present lens can focus incident plane waves on the opposite side with high convergence, and its operating frequency range is rather broadband, spanning from 6 to 16 GHz. Besides, the all-dielectric honeycomb-like lens is lightweight with a mass density of 0.23 g/cm3, and its broadband transmittance is higher than the reported cases consisting of metallic metamaterial or gradient photonic crystal structures. A prototype of the lens is fabricated by using 3D printing techniques, on which the electric near-field distribution and far-field radiation pattern measurements have been carried out, and the aforementioned performances were demonstrated experimentally. It was also observed that for two point sources placed at the edge of the lens whose intersection angle with the center of the lens is 90°, the far-field radiation pattern was still kept highly directional, which means that the lens can generate two highly directional beams simultaneously, and is an efficient double input-double output device.

15.
Opt Lett ; 43(12): 2764-2767, 2018 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-29905683

RESUMEN

Microwave absorber with broadband absorption and thin thickness is one of the main research interests in this field. A flexible ultrathin and broadband microwave absorber comprising multiwall carbon nanotubes, spherical carbonyl iron, and silicone rubber is fabricated in a newly proposed pyramidal spatial periodic structure (SPS). The SPS with equivalent thickness of 3.73 mm covers the -10 dB and -15 dB absorption bandwidth in the frequency range 2-40 GHz and 10-40 GHz, respectively. The excellent absorption performance is achieved by concentration and dissipation of the electromagnetic field inside different parts of the magnetic-dielectric lossy protrusions in different frequency ranges.

16.
Virology ; 516: 189-195, 2018 03.
Artículo en Inglés | MEDLINE | ID: mdl-29407376

RESUMEN

Between May 2015 and May 2017, 496 animals (473 murine rodents and 23 house shrews) were captured in six regions of China. A total of 22.8% (113/496) of throat swabs, 29.1% (142/488) of fecal samples and 23.8% (54/227) of serum samples tested positive for rodent torque teno virus 3 (RoTTV3). The positive rate in Rattus norvegicus was higher than the rate in Rattus tanezumi and Rattus losea. Of 23 house shrews, one throat swab and one serum sample were positive for RoTTV3. Ten murine rodents were simultaneously positive for RoTTV3 in throat swab, fecal and serum samples. Phylogenetic analysis showed that the 12 near-full length genomes of RoTTVs sequences obtained in this study represented a novel RoTTV genotype (RoTTV3). In conclusion, high prevalence rates of RoTTV3 were found in three common murine rodents in China, and the RoTTV3 obtained in this study were classified as a novel genotype of RoTTV.


Asunto(s)
Reservorios de Enfermedades/virología , Filogenia , Roedores/virología , Musarañas/virología , Torque teno virus/clasificación , Torque teno virus/aislamiento & purificación , Animales , China , Genoma Viral , Genotipo , Ratones , Ratas , Torque teno virus/genética
17.
ACS Appl Mater Interfaces ; 10(9): 8205-8213, 2018 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-29424525

RESUMEN

Ultralight and highly elastic reduced graphene oxide (RGO)/lignin-derived carbon (LDC) composite aerogels with aligned micron-sized pores and cell walls are prepared using a facile freeze-drying method. The presence of a small fraction of LDC in the cell walls enhances the interfacial polarization effect while almost maintaining the amount of charge carriers and conductivity of the cell walls, greatly boosting the wave absorption capability of the cell walls. RGO/LDC aerogels also show a greater number of large cell walls with better integrity than RGO aerogels, further improving the multiple reflection ability of the aligned cell walls. Synergistic effects of the multiphase cell walls and the preferred microstructures of the RGO/LDC aerogels lead to their high electromagnetic interference (EMI) shielding effectiveness of 21.3-49.2 dB at an ultralow density of 2.0-8.0 mg/cm3. This corresponds to the surface-specific SE (SE divided by density and thickness) up to 53 250 dB·cm2/g, which is higher than the values reported for other carbon- and metal-based shields. Furthermore, the critical roles that microstructures play in determining the EMI shielding performance are directly revealed by comparing the shielding performance in directions parallel and normal to cell walls, as well as in an in situ compression process.

18.
ACS Appl Mater Interfaces ; 9(49): 43179-43187, 2017 Dec 13.
Artículo en Inglés | MEDLINE | ID: mdl-29148712

RESUMEN

Ultra-broad-band electromagnetic absorption materials and structures are increasingly attractive for their critical role in competing with the advanced broad-band electromagnetic detection systems. Mechanically soft and weak wax-based materials composites are known to be insufficient to serve in practical electromagnetic absorption applications. To break through such barriers, here we developed an innovative strategy to enable the wax-based composites to be robust and repairable meta-structures by employing a three-dimensional (3D) printed polymeric patterned shell. Because of the integrated merits from both the dielectric loss wax-based composites and mechanically robust 3D printed shells, the as-fabricated meta-structures enable bear mechanical collision and compression, coupled with ultra-broad-band absorption (7-40 and 75-110 GHz, reflection loss  smaller than -10 dB) approaching state-of-the-art electromagnetic absorption materials. With the assistance of experiment and simulation methods, the design advantages and mechanism of employing such 3D printed shells for substantially promoting the electromagnetic absorption performance have been demonstrated. Therefore, such universal strategy that could be widely extended to other categories of wax-based composites highlights a smart stage on which high-performance practical multifunction meta-structures with ultra-broad-band electromagnetic absorption could be envisaged.

19.
ACS Appl Mater Interfaces ; 9(41): 36119-36129, 2017 Oct 18.
Artículo en Inglés | MEDLINE | ID: mdl-28945066

RESUMEN

Due to substantial development of electronics and telecommunication techniques, materials with electromagnetic interference (EMI) shielding performance are significant in alleviating the interference impacts induced from a remarkable variety of devices. In the work, we propose novel sandwich structures for manipulating the EM wave transport, which holds unique EMI shielding features of frequency selectivity. By employing electrical and magnetic loss spacers, the resultant sandwich structures are endowed with tunable EMI shielding performance, showing substantial improvements in overall shielding effectiveness along with pronounced shielding peak shift. The mechanisms suggest that the multiple interfaces, electromagnetic loss media, and changes of representative EM wavelength could be critical roles in tailoring the EMI shielding performance. The results provide a versatile strategy that could be extended in other frequency ranges and various types of sandwich structures, promising great opportunities for designing and fabricating advanced electromagnetic attenuation materials and devices.

20.
ACS Appl Mater Interfaces ; 9(37): 32211-32219, 2017 Sep 20.
Artículo en Inglés | MEDLINE | ID: mdl-28846376

RESUMEN

Flexible waterborne polyurethane (WPU)/silver nanowire (AgNW) nanocomposites with unidirectionally aligned micrometer-sized pores are fabricated using a facile freeze-drying process, and their dimensions, densities, and AgNW contents are easily controllable. The high-aspect-ratio AgNWs are well-dispersed in the nanocomposite cell walls, giving the nanocomposites good compression strength and excellent electrical conductivity even at very low densities. The large conductivity mismatch between the AgNWs and WPU also induces substantial interfacial polarization that benefits the absorption of electromagnetic (EM) waves, whereas the aligned cell walls promote multireflections of the waves in the porous architectures, further facilitating the absorption. The synergistic actions of the AgNWs, WPU, and unidirectionally aligned pores lead to ultrahigh EM shielding performance. The X-band shielding effectiveness (SE) of the nanocomposites is 64 and 20 dB at the densities of merely 45 and 8 mg/cm3, respectively, and ultrahigh surface specific SE of ∼1087 dB cm3/(g mm) is achieved with only 0.027 vol % AgNWs, demonstrating that they are promising ultralight, flexible, mechanically robust, high-performance EM shielding materials.

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