The temperature coefficient of resonant frequency (τf) is a key parameter for microwave dielectric ceramics, and it is usually regarded as a temperature-independent constant over a wide temperature range. However, the present theoretical prediction shows that the resonant frequency (f0) first increases then decreases with temperature, and τf decreases monotonously in Al2O3–TiO2 composite with small τf, which fits the experimental data very well. The nonlinear variation of f0 with temperature and temperature-dependent τf are attributed to the temperature-sensitive permittivity (εr) and τf of the constituting phases and also dependent on the dielectric mixing rule that the composite obeys. Such temperature-dependent dielectric behaviors are predicted to be common in microwave dielectric composites with small τf, and the negligence of them probably conceals the real large variation of f0 with temperature and seriously misleads the practical applications. Therefore, it is strongly suggested to understand the real temperature dependence of f0 and τf in microwave dielectric composites by measuring f0 at more temperatures with a smaller interval, so that the central frequency shift can be correctly evaluated for the resonator units and devices where the microwave dielectric composites are utilized. Furthermore, the nonlinear variation of f0 with temperature and temperature dependence of τf are expected to be suppressed by microstructural engineering and adopting more suitable constituting phases.
A lack of contraction of cerebral microarterioles to Ang II ("resilience") depends on cyclooxygenase (COX) and lipocalin type prostaglandin D sythase L-PGDS producing PGD2 that activates prostaglandin D type 1 receptors (DP1Rs) and nitric oxide synthase (NOS).Contractions were assessed in isolated, perfused vessels and NO by fluorescence microscopy.The mRNAs of penetrating intraparenchymal cerebral microarterioles versus renal afferent arterioles were >3000-fold greater for L-PGDS and DP1R and 5-fold for NOS III and COX 2. Larger cerebral arteries contracted with Ang II. However, cerebral microarterioles were entirely unresponsive but contracted with endothelin 1 and perfusion pressure. Ang II contractions were evoked in cerebral microarterioles from COX1 -/- mice or after blockade of COX2, L-PGDS or NOS and in deendothelialized vessels but effects of deendothelialization were lost during COX blockade. NO generation with Ang II depended on COX and also was increased by DP1R activation.The resilience of cerebral arterioles to Ang II contractions is specific for intraparenchymal microarterioles and depends on endothelial COX1 and two products that are metabolized by L-PGDS to generate PGD2 that signals via DP1Rs and NO.
This article reports for the first time a stiffness-adjustable resonant accelerometer using the distributed electrostatic drive scheme, which has great potential in realizing high-frequency mode drive and improving the sensitivity of resonant accelerometers. First, a resonant accelerometer consisting of a sensitive mass block, a resonant beam, a driving electrode, two regulating electrodes, and a sensing electrode is designed, fabricated, and characterized. Then, the performance of the resonant beam in the resonant accelerometer has been fully assessed through its open-loop responses, with sensitivities of 85, 134, and 135 Hz/g based on the first three bending vibration modes. Through theoretical prediction and experimental measurement, it is found that with the increase of control voltage applied to the regulating electrodes, the sensitivity and signal-to-noise ratio (SNR) of resonant acceleration can be effectively improved. Typically, when the resonant beam works near the critical buckling, the sensitivity based on the first mode can be increased from 85 to 4920 Hz/g. Finally, the electrostatic force caused by the control voltage is experimentally proved to overcome the frequency-amplitude dependence caused by the stiffness hardening. The results of this article provide theoretical guidance and experimental support for the design of linear resonant accelerometers with high sensitivity.
• Low- ε r limit for dense inorganic materials was discussed. • Parameters dominating low ε r were analyzed. • Difference between dielectric constant for crystalline and amorphous materials was discussed. • It is discussed how to achieve ultralow ε r in dense inorganic materials.
Abstract It is well accepted that junctophilin (JPHs) isoforms act as a physical bridge linking plasma membrane and endoplasmic reticulum (ER) for channel crosstalk in excitable cells. Our purpose is to investigate whether JPHs are involved in the proper communication between Ca 2+ influx and subsequent Ca 2+ amplification in pancreatic beta cells, thereby participating in regulating insulin secretion. The expression of JPH isoforms was examined in human and mouse pancreatic tissues, and JPH3 expression was found in both the beta cells. In mice, knockdown of Jph3 (si- Jph3 ) in islets decreased glucose-stimulated insulin secretion (GSIS) accompanied by mitochondrial function impairment. Si- Jph3 lowered the insulin secretory response to Ca 2+ signaling in the presence of glucose, and reduced [Ca 2+ ] c transient amplitude triggered by caffeine. Si- Jph3 also attenuated mitofusin 2 expression, thereby disturbing the spatial organization of ER–mitochondria contact in islets. These results suggest that the regulation of GSIS by the K ATP channel-independent pathways is partly impaired due to decrease of JPH3 expression in mouse islets. JPH3 also binds to type 2 ryanodine receptors (RyR2) in mouse and human pancreatic tissues, which might contribute to Ca 2+ release amplification in GSIS. This study demonstrates some previously unrecognized findings in pancreatic tissues: (1) JPH3 expresses in mouse and human beta cells; (2) si- Jph3 in mouse primary islets impairs GSIS in vitro ; (3) impairment in GSIS in si- Jph3 islets is due to changes in RyR2-[Ca 2+ ] c transient amplitude and ER-mitochondria contact.
The nonlinear distortion caused by the interaction between chromatic dispersion and direct detection reduces the capacity of optical discrete multi-tone system beyond dozens of kilometers. The proposed nonlinear equalizer compensated the distortion and increased the capacity by up to 50%.
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