Current Issue : April - June Volume : 2019 Issue Number : 2 Articles : 5 Articles
This paper presents a feasibility study for a non-wearable, conformal, low cost, and\ndisposable antenna-based sensor for non-invasive hydration monitoring using sweat. It is composed\nof a patch antenna implemented on a cellulose filter paper substrate and operating in the range\n2â??4 GHz. The paper substrate can absorb liquids, such as sweat on the skin, through two slots\nincorporated within the antenna structure. Thus, the substrate dielectric properties are altered\naccording to the properties of the absorbed liquid. Changes in reflection-based measurements are\nused to analyze salt solutions and artificial sweat, specifically the amount of sampled solution and\nthe sodium chloride (NaCl) concentration. Using the shift in resonant frequency and magnitude of\nthe reflection coefficient, NaCl concentrations in the range of 8.5â??200 mmol/L, representing different\nhydration states, are detected. The measurements demonstrate the feasibility of using microwave\nbased measurements for hydration monitoring using sweat....
It is common experience that our eyes do not perceive significant changes in\ncolor when we observe for long time an object continuously exposed to light.\nWe always see plants to be green in summer until in autumn factors external\nto our vision, such as changes in the length of daylight and temperature,\ncause the break-down of chlorophyll and, in turn, spectacular changes in\nplantâ??s colors. Likewise, the photocurrent produced in solar panels or field\neffect transistors achieves a steady state magnitude shortly after the start of\nthe illumination. The steady state photocurrent lasts until the illumination\nstops. Understanding the origin of the steady state response of a device or\nlight harvesting (LH) system to illumination with electromagnetic (EM)\nwaves motivates the research presented in this work. In our experiments, we\nused capacitors as LH systems and illuminated them with infrared (IR) light\nover an 80 hours time period. We investigated the interaction between light\nand matter by monitoring versus time the voltage output of the capacitors. By\ncombining modeling and experimental observations, we concluded that the\nsteady state voltage is established soon after the start of the illumination as\nthe consequence of the law of conservation of energy. We also found that the\nmagnitude of the voltage in the steady state depends on the power and period\nof the illuminating IR light, and on the capacitance of the capacitor. When\nlightâ??s power undergoes fluctuations, also the voltage produced by the capacitor\nand the surface charge density on the capacitors do so. These findings\nsuggest that the law of conservation of energy has a significant repercussion\nwhen light is absorbed by matter in the steady state, for example in the mechanism\nof vision in vertebrates. Likewise, these findings are true when light\nis emitted from matter, for example in the mechanism of formation of the\nCosmic Microwave Background (CMB)....
Esters are common chemicals with extensive applications in medicine, biology,\nchemistry, and material sciences [1]-[7]. Esters used not only as solvents but also\nare in perfumes, essential oils, agriculture and food flavorings, antioxidant, plastics,\ndetergents, and for many other purposes. Isoamyl acetate (odor of banana),\nethyl butanoate (odor of mango), methyl 2-methylbutanoate (odor of pineapple),\nvitamin C, cocaine, etc., are some common interesting examples occurring\nin the nature. The enormous use of transition metal complexes to activate organic\nmolecules makes them viable visions for developing catalytic processes\nwith high selectivity and atom economy. This work focusses to find a facile way\nof making esters by microwave irradiated cross-coupling reaction of carboxylic\nacids, allyl type halides, in the presence of palladium-catalyst (Scheme 1) and\napply that effective cross coupling method to synthesize arachidonic acid esters,\nand folic acid esters, etc....
In this paper, a triple-band dual-sense circularly polarized (CP) hybrid dielectric resonator\nantenna is proposed. A modified hexagonal dielectric resonator (DR) is top-loaded with a square\nmicrostrip ring (SMR). A vertical-tapered-strip connected to a 50-ohms microstrip line is used to excite\nthe proposed antenna. It is found that the lower and central CP bands correspond to left-handed\ncircular polarization and are produced by the TM11 and TE111 modes of the SMR and modified\nhexagonal DR, respectively. The upper CP band is formed by the combination of the quasi-TM21\nmode of the SMR and quasi-TE111 mode of the DR that exhibits right-handed circular polarization.\nThe measurement results of the fabricated prototype show triple-band response for |S11| < -10 dB\nwith impedance bandwidths (IBWs) of 17.4% (1.75-2.03 GHz), 28.13% (2.23-2.96 GHz), and 2.97%\n(3.65-3.76 GHz) in the lower, central, and upper bands, respectively. The measured 3 dB axial ratio\nbandwidths lying within -10 dB IBWs are 3.69% (1.86-1.93 GHz), 5.46% (2.670-2.82 GHz), and 2.15%\n(3.68-3.76 GHz) along with the peak gains of 5 dBic, 5.28 dBic, and 2.36 dBic in the lower, central, and\nupper bands, respectively....
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