7,250 research outputs found
Third-order Intermodulation Reduction in Mobile Power Amplifiers by the First Stage Bias Control
In this paper, the third order intermodulation distortion (IMD3) of three-stage power amplifier (PA) is analyzed using the Volterra series. The analysis explains how the total IMD3 of the three-stage power amplifier can be reduced by the first-stage bias condition. The three-stage PA, which is fabricated using InGaP/GaAs hetero-junction bipolar transistor (HBT), operates with an optimized first driver stage bias for higher P1dB and good gain flatness. The power amplifier has been designed for 1626.5 MHz~1660.5 MHz satellite mobile communications. With π/4 DQPSK modulation signals, this PA can deliver a highly linear output power of 33 dBm from 3.6V supply voltage. At 33 dBm output power, it shows a gain of 31.9 dB, a power-added efficiency (PAE) of 39.8%, an adjacent channel power ratio (ACPR) of -28.2 dBc at a 31.25 KHz offset frequency
Protective Effect of Purple Sweet Potato (Ipomoea batatas Linn, Convolvulaceae) on Neuroinflammatory Responses in Lipopolysaccharide-Stimulated Microglial Cells
Purpose: To evaluate the protective effects of purple sweet potato (Ipomoea batatas Linn, Convolvulaceae) extract (IBE) in stimulated BV-2 microglial cells and its anti-oxidant properties.Methods: Cell viability assessment was performed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) assay. Lipopolysaccharide (LPS) was used to activate BV-2 microglia. Nitric oxide (NO) levels were measured using Griess assay. Inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 expressional levels were measured by Western blot analysis. Tumor necrosis factor-alpha (TNF-α) production was evaluated by enzyme-linked immunosorbent assay (ELISA). Antioxidantproperties were evaluated by 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay.Results: LPS-activated excessive release of NO in BV-2 cells was significantly inhibited by IBE (p<0.001 at 100 µg/mL). Increased production of inflammatory mediators such as iNOS, COX-2 and TNF-α (p < 0.01 and p < 0.001 at 100 and 200 µg/ml, respectively) was attenuated by IBE concentration-dependently. IBE also scavenged DPPH radicals in a dose-dependent manner (p < 0.05 at 10 ìg/ml and p < 0.001 at 20 - 200 µg/ml).Conclusion: These results indicate that IBE attenuated neuroinflammatory responses in LPS-activated BV-2 microglia by inhibiting excessive production of pro-inflammatory mediators such as NO, iNOS, COX-2 and TNF-α. The anti-neuroinflammatory potential of IBE may be related to its strong antioxidant properties.Keywords: Ipomoea batatas, DPPH radicals, Anti-oxidant, Neuroinflammation, BV-2 microglia, Nitric oxide
Dramatic improvement of strain hardening and ductility to 95% in highly-deformable high-strength duplex lightweight steels
Ferrite + austenite duplex lightweight steels have been actively developed by adding low-density Al for overcoming a limitation of stiffness deterioration by a traditional approach to obtain a weight reduction. Multiple-stage deformation mechanism in lightweight steels, i.e., simultaneous formation of deformation-induced martensite and deformation twin and additional plasticity by twinning, has been nominated as an attractive strategy, but shows a steady flow behavior with early plastic instability. Here, we present a newly designed Fe-0.3C-9Mn-5Al steel in order to obtain an optimal level of stability of austenite and a resultant outstanding combination of tensile strength and ductility, e.g., 874 MPa and 72%, together with sufficiently high strain hardening. These enhanced properties are attributed to the decreased austenite stability by controlling the austenite size and alloying partitioning due to variation in austenite fraction inside duplex microstructures. The present work gives a promise for structural applications requiring both reduced specific weight and remarkable deformability. ? 2017 The Author(s).114Ysciescopu
Immunological Significance of HMGB1 Post-Translational Modification and Redox Biology
© Copyright © 2020 Kwak, Kim, Lee, Kim, Son and Shin. Most extracellular proteins are secreted via the classical endoplasmic reticulum (ER)/Golgi-dependent secretion pathway; however, some proteins, including a few danger-associated molecular patterns (DAMPs), are secreted via non-classical ER/Golgi-independent secretion pathways. The evolutionarily conserved high mobility group box1 (HMGB1) is a ubiquitous nuclear protein that can be released by almost all cell types. HMGB1 lacks signal peptide and utilizes diverse non-canonical secretion mechanisms for its extracellular export. Although the post-translational modifications of HMGB1 were demonstrated, the oxidation of HMGB1 and secretion mechanisms are not highlighted yet. We currently investigated that peroxiredoxins I and II (PrxI/II) induce the intramolecular disulfide bond formation of HMGB1 in the nucleus. Disulfide HMGB1 is preferentially transported out of the nucleus by binding to the nuclear exportin chromosome-region maintenance 1 (CRM1). We determined the kinetics of HMGB1 oxidation in bone marrow-derived macrophage as early as a few minutes after lipopolysaccharide treatment, peaking at 4 h while disulfide HMGB1 accumulation was observed within the cells, starting to secrete in the late time point. We have shown that HMGB1 oxidation status, which is known to determine the biological activity in extracellular HMGB1, is crucial for the secretion of HMGB1 from the nucleus. This review summarizes selected aspects of HMGB1 redox biology relevant to the induction and propagation of inflammatory diseases. We implicate the immunological significance and the need for novel HMGB1 inhibitors through mechanism-based studies
Monte Carlo Simulation of Sinusoidally Modulated Superlattice Growth
The fabrication of ZnSe/ZnTe superlattices grown by the process of rotating
the substrate in the presence of an inhomogeneous flux distribution instead of
successively closing and opening of source shutters is studied via Monte Carlo
simulations. It is found that the concentration of each compound is
sinusoidally modulated along the growth direction, caused by the uneven arrival
of Se and Te atoms at a given point of the sample, and by the variation of the
Te/Se ratio at that point due to the rotation of the substrate. In this way we
obtain a ZnSeTe alloy in which the composition varies
sinusoidally along the growth direction. The period of the modulation is
directly controlled by the rate of the substrate rotation. The amplitude of the
compositional modulation is monotonous for small angular velocities of the
substrate rotation, but is itself modulated for large angular velocities. The
average amplitude of the modulation pattern decreases as the angular velocity
of substrate rotation increases and the measurement position approaches the
center of rotation. The simulation results are in good agreement with
previously published experimental measurements on superlattices fabricated in
this manner
Grapefruit Seed Extract as a Natural Derived Antibacterial Substance against Multidrug-Resistant Bacteria
Multidrug-resistant (MDR) bacteria are increasing due to the abuse and misuse of antibiotics, and nosocomial infections by MDR bacteria are also increasing. The aim of this study was to
identify new substances that can target MDR bacteria among 12 plant extracts that are known to have
antibacterial effects. The experiments were performed by the disk diffusion test and microdilution
minimum inhibitory concentration (MIC) test, as described by the Clinical and Laboratory Standards
Institute (CLSI). By screening against methicillin-sensitive Staphylococcus aureus (MSSA), grapefruit
seed extract (GSE) was selected from 12 plant extracts for subsequent experiments. GSE showed
antibacterial effects against methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus
(VRSA) in the disk diffusion test. Even at the lowest concentration, GSE showed antibacterial activity
in the microdilution MIC test. As a result, we can conclude that GSE is a naturally derived antibacterial substance that exhibits a favorable antibacterial effect even at a very low concentration, so it is a
good candidate for a natural substance that can be used to prevent or reduce nosocomial infections
as coating for materials used in medical contexts or by mixing a small amount with other material
Escape from adamantane: Scaffold optimization of novel P2X7 antagonists featuring complex polycycles
The adamantane scaffold, despite being widely used in medicinal chemistry, is not devoid of problems. In the recent years we have developed new polycyclic scaffolds as surrogates of the adamantane group with encouraging results in multiple targets. As an adamantane scaffold is a common structural feature in several P2X7 receptor antagonists, herein we report the synthesis and pharmacological evaluation of multiple replacement options of adamantane that maintain a good activity profile. Molecular modeling studies support the binding of the compounds to a site close to the central pore, rather than to the ATP-binding site and shed light on the structural requirements for novel P2X7 antagonists
Estimation of Effective Plant Area Index for South Korean Forests Using LiDAR System
Light Detection and Ranging (LiDAR) systems can be used to estimate both vertical and horizontal forest structure. Woody components, the leaves of trees and the understory can be described with high precision, using geo-registered 3D-points. Based on this concept, the Effective Plant Area Indices (PAIe) for areas of Korean Pine (Pinus koraiensis), Japanese Larch (Larix leptolepis) and Oak (Quercus spp.) were estimated by calculating the ratio of intercepted and incident LIDAR laser rays for the canopies of the three forest types. Initially, the canopy gap fraction (GLiDAR) was generated by extracting the LiDAR data reflected from the canopy surface, or inner canopy area, using k-means statistics. The LiDAR-derived PAIe was then estimated by using GLIDAR with the Beer-Lambert law. A comparison of the LiDAR-derived and field-derived PAIe revealed the coefficients of determination for Korean Pine, Japanese Larch and Oak to be 0.82, 0.64 and 0.59, respectively. These differences between field-based and LIDAR-based PAIe for the different forest types were attributed to the amount of leaves and branches in the forest stands. The absence of leaves, in the case of both Larch and Oak, meant that the LiDAR pulses were only reflected from branches. The probability that the LiDAR pulses are reflected from bare branches is low as compared to the reflection from branches with a high leaf density. This is because the size of the branch is smaller than the resolution across and along the 1 meter LIDAR laser track. Therefore, a better predictive accuracy would be expected for the model if the study would be repeated in late spring when the shoots and leaves of the deciduous trees begin to appear
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