The need for miniaturization and weight reduction of GPS patch antennas has prompted the search for new microwave dielectric materials. In this study, a sol–gel method was used to prepare Zn(1?x)MgxAl2O4 thin films and fabricate GPS patch antennas at a low annealing temperature (700 °C). X-ray diffraction (XRD) patterns, field emission scanning electron microscopy images, Fourier transform infrared spectra, and optical band gap analyses confirmed the nanostructure of (Mg/Zn)Al2O4. The XRD patterns displayed the characteristic peaks of (Mg/Zn)Al2O4 with a face-centered cubic structure. Mg addition decreased the crystallite size, surface morphology, and lattice parameters of the resultant films, evidently affecting their density and dielectric constant (?r). Based on the material investigated and microwave antenna theory, GPS patch antennas were fabricated using Zn(1?x)MgxAl2O4 and then studied using a PNA series network analyzer. The fabricated patch antennas with different ?r ceramics decreased in size from 12.5 to 10.8 cm2. The patch antennas resonated at a frequency of 1.570 GHz and provided a return loss bandwidth between ?16.6 and ?20.0 dB; their bandwidth also improved from 90 to 255 MHz. The GPS patch antenna fabricated from Zn0.70Mg0.30Al2O4 showed an excellent combination of return loss (?20.0 dB), small size (10.8 cm2), and wide bandwidth (255 MHz). Therefore, addition of Mg improves antenna performance and decreases the dimensions of the device. 相似文献
It remains highly desired but a great challenge to achieve atomically dispersed metals in high loadings for efficient catalysis. Now porphyrinic metal–organic frameworks (MOFs) have been synthesized based on a novel mixed‐ligand strategy to afford high‐content (1.76 wt %) single‐atom (SA) iron‐implanted N‐doped porous carbon (FeSA‐N‐C) via pyrolysis. Thanks to the single‐atom Fe sites, hierarchical pores, oriented mesochannels and high conductivity, the optimized FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and state‐of‐the‐art Pt/C, in both alkaline and more challenging acidic media. More far‐reaching, this MOF‐based mixed‐ligand strategy opens a novel avenue to the precise fabrication of efficient single‐atom catalysts. 相似文献
The dicyanamide‐bridged polymers with Schiff‐base ligand, [CoNaL(dca)]n ( 1 ) and [Mn2L(dca)2]n ( 2 ) [H2L = bis(3‐methoxysalicylidene)benzene‐1,2‐diamine, dca = dicyanamide] were synthesized and characterized by elemental analyses, IR spectrroscopy and single‐crystal X‐ray diffraction. The solid‐state structures reveal that polymer 1 has double dca bridged loop‐like 1D chains, in which the heterodinuclear Co2+‐Na+ units (LCoNa) are bridged by dca with coordination mode μ1,3,5. In polymer 2 , homodinuclear Mn2+‐Mn2+(LMnMn) units are linked by dca in μ1,5‐bridging mode to form 2D planes. Magnetic susceptibility studies on 2 reveals antiferromagnetic coupling interactions between the adjacent Mn2+ ions in the LMnMn unit. 相似文献
MGMT protein, which has been associated with resistance to antitumor alkylation drugs for many patients, is a very useful prognostic marker to provide a guide for therapeutic decisions. Considering the large number of cellular samples that have to be handled daily at the hospitals, it is thus important to develop a rapid and simple analytical method to distinguish MGMT activity in different types of cells. In this paper, we describe a MGMT‐activated fluorescence turn‐on probe for the rapid no‐wash imaging of MGMT in living cells. The probe consists of a specific MGMT suicide pseudosubstrate, O6‐benzyl‐guanine and an environment‐sensitive fluorophore, SBD. In the presence of MGMT, the enzyme transfers SBD to the protein active site where the hydrophobic surrounding causes the fluorophore to exhibit more than 50‐fold fluorescence enhancement. With this probe, bright fluorescence was observed for MGMT‐positive, Hela S3 and MCF‐7 cells, while MGMT‐deficient CHO cells displayed no fluorescence. We believe that this fluorescence activation probe design can also be extended to detect other transferases, for which there are still no effective methods to image them in living cells. 相似文献
A Re2O7 catalyzed cycloetherification of monoallylic diols is described. The reaction features short reaction time, mild reaction conditions and exclusive E selectivity. A wide range of monoallylic alcohols with alkyl or aryl substituents on olefin smoothly undergo ring closure to deliver corresponding oxa-heterocycles. The reaction is also operationally simple and not sensitive to air and moisture. 相似文献
Four novel stilbene-twelve alkyl quaternary ammonium salts 5a–d were synthesized. All synthesized compounds were characterized by FT-IR, 1H-NMR and elemental analysis. Compounds 5a–d showed efficient whitening effect on cotton fiber and high fastness. Furthermore, compound 5c showed better stability to light than C186 in aqueous solution. The preliminary biological experiment demonstrated compounds 5a–d possessed significant antibacterial activities. Among them, compound 5d turned out to be the most active compound against Candida albicans with MIC50 4 μg/mL as well as E. coli with MIC50 16 μg/mL. 相似文献
The directional drifting of particles/molecules with broken symmetry has received increasing attention. Through molecular dynamics simulations, we investigate the effects of various solvents on the time-dependent directional drifting of a particle with broken symmetry. Our simulations show that the distance of directional drift of the asymmetrical particle is reduced while the ratio of the drift to the mean displacement of the particle is enhanced with increasing mass, size, and interaction strength of the solvent atoms in a short time range. Among the parameters considered, solvent atom size is a particularly influential factor for enhancing the directional drift of asymmetrical particles, while the effects of the interaction strength and the mass of the solvent atoms are relatively weaker. These findings are of great importance to the understanding and control of the Brownian motion of particles in various physical, chemical, and biological processes within finite time spans. 相似文献
C-11 (2-((7-Ethyl-3-methyl-8-(4-(2-(methyl(pyridin-2-yl)-amino)-ethoxy)phenyl)-2,6-dioxo-2,3,6,7-tetrahydro-1H-purin-1-yl)methyl)benzonitrile-one hydrochloride), which is based on the structure of rosiglitazone, was first synthesized in our laboratory and shown to be a promising anti-obesity drug candidate in our previous pharmacological study. Considering the importance of metabolic fate in vivo in the further development of drug candidates during early drug discovery, it is essential to characterize the metabolism of C-11 in vivo. In this work, a method based on ultra-high performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) was successfully developed to investigate the in vivo metabolic profile of C-11 in rats. Rat urine, feces, and plasma samples were collected from male Sprague–Dawley rats after intravenous administration of C-11 in a single dose of 30 mg kg−1 body weight. Besides the parent drug, a total of 25 metabolites (including 18 phase I and 7 phase II metabolites) were detected and tentatively identified by comparing their mass spectrometry profiles with those of C-11. This enabled the metabolic pathways of C-11 to be proposed for the first time. Our results revealed that N-depyridinylation, N-demethylation, hydroxylation, glucuronidation, and sulfate conjugation are the predominant metabolic pathways of C-11 in rats. The present study provides systematic information on the metabolism of C-11 in vivo, which should lead to a better understanding of its safety and mechanism of action.