GaN-Based RF Power Devices and Amplifiers Mishra, Umesh K.; Shen, Likun; Kazior, Thomas E. ...
Proceedings of the IEEE,
02/2008, Volume:
96, Issue:
2
Journal Article
Peer reviewed
The rapid development of the RF power electronics requires the introduction of wide bandgap material due to its potential in high output power density, high operation voltage and high input ...impedance. GaN-based RF power devices have made substantial progresses in the last decade. This paper attempts to review the latest developments of the GaN HEMT technologies, including material growth, processing technologies, device epitaxial structures and MMIC designs, to achieve the state-of-the-art microwave and millimeter-wave performance. The reliability and manufacturing challenges are also discussed.
Immiscible fluid‐fluid displacement in permeable media is important in many subsurface processes, including enhanced oil recovery and geological CO2 sequestration. Controlled by capillary and viscous ...forces, displacement patterns of one fluid displacing another more viscous one exhibit capillary and viscous fingering, and crossover between the two. Although extensive studies investigated viscous and capillary fingering in porous media, a few studies focused on the crossover in rough fractures, and how viscous and capillary forces affect the crossover remains unclear. Using a transparent fracture‐visualization system, we studied how the two forces impact the crossover in a horizontal rough fracture. Drainage experiments of water displacing oil were conducted at seven flow rates (capillary number log10Ca ranging from −7.07 to −3.07) and four viscosity ratios (M=1/1000,1/500,1/100 and 1/50). We consistently observed lower invading fluid saturations in the crossover zone. We also proposed a phase diagram for the displacement patterns in a rough fracture that is consistent with similar studies in porous media. Based on real‐time imaging and statistical analysis of the invasion morphology, we showed that the competition between capillary and viscous forces is responsible for the saturation reduction in the crossover zone. In this zone, finger propagation toward the outlet (characteristic of viscous fingering) as well as void‐filling in the transverse/backward directions (characteristic of capillary fingering), are both suppressed. Therefore, the invading fluid tends to occupy larger apertures with higher characteristic front velocity, promoting void‐filling toward the outlet with thinner finger growth and resulting in a larger volume of defending fluid left behind.
Key Points
Lower invading fluid saturations were observed in the crossover zone and a phase diagram was obtained for rough fracture
The saturation reduction in the crossover zone is induced by the significant suppression of both viscous and capillary fingerings
In the crossover, invading fluid occupies larger aperture spaces with higher front velocity, stimulating void‐filling toward the outlet
The coronavirus disease 2019 (COVID-19) pandemic is an exceptional public health crisis that demands the timely creation of new therapeutics and viral detection. Owing to their high specificity and ...reliability, monoclonal antibodies (mAbs) have emerged as powerful tools to treat and detect numerous diseases. Hence, many researchers have begun to urgently develop Ab-based kits for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Ab drugs for use as COVID-19 therapeutic agents. The detailed structure of the SARS-CoV-2 spike protein is known, and since this protein is key for viral infection, its receptor-binding domain (RBD) has become a major target for therapeutic Ab development. Because SARS-CoV-2 is an RNA virus with a high mutation rate, especially under the selective pressure of aggressively deployed prophylactic vaccines and neutralizing Abs, the use of Ab cocktails is expected to be an important strategy for effective COVID-19 treatment. Moreover, SARS-CoV-2 infection may stimulate an overactive immune response, resulting in a cytokine storm that drives severe disease progression. Abs to combat cytokine storms have also been under intense development as treatments for COVID-19. In addition to their use as drugs, Abs are currently being utilized in SARS-CoV-2 detection tests, including antigen and immunoglobulin tests. Such Ab-based detection tests are crucial surveillance tools that can be used to prevent the spread of COVID-19. Herein, we highlight some key points regarding mAb-based detection tests and treatments for the COVID-19 pandemic.
The flow of multiple immiscible fluids in disordered porous media is important in many natural processes and subsurface applications. The pore‐scale disorder affects the fluid invasion pathways ...significantly and induces the transitions of displacement patterns in porous media. Extensive studies focus on pattern transitions affected by disorder under quasistatic or dynamic conditions, but how the disorder controls the pattern transitions from capillary‐dominated regime to viscous‐dominated regime is not well understood. Here, we combine microfluidic experiments and theoretical analysis to investigate the role of disorder in fluid displacement. We perform drainage experiments with four different disorders under six flow rate conditions and show that increasing disorder destabilizes displacement fronts for all flow rates considered. Based on the scaling analysis of pore‐filling events, we propose a theoretical model that describes the pattern transitions from compact displacement to capillary to viscous fingering as functions of disorder and capillary number. The effects of disorder on both capillary and viscous forces are quantified within the theoretical model. The phase diagram predicted by this model agrees well with our experimental results. We further elucidate the role of disorder in fluid displacement via energy conversion and dissipation. We find that increasing disorder enhances the capillary instabilities and induces more energy dissipated in a capillary‐dominated regime, with the dissipation ratio increasing from 28.3% to 56.7%. Our work extends the classic phase diagram to consider the effect of disorder and provides a better understanding of the impact of the disorder on flow behaviors by energy dissipation.
Key Points
We propose a theoretical model to describe the transitions of displacement patterns as functions of disorder and capillary number
Effects of disorder on both capillary and viscous forces are considered in the model and the phase diagram agrees with experiments
Higher disorder destabilizes fronts and dissipates more energy, with the dissipation ratio increasing from 28.3% to 56.7%
Li−CO2 batteries have received significant attention owing to their advantages of combining greenhouse gas utilization and energy storage. However, the high kinetic barrier between gaseous CO2 and ...the Li2CO3 product leads to a low operating voltage (<2.5 V) and poor energy efficiency. In addition, the reversibility of Li2CO3 has always been questioned owing to the introduction of more decomposition paths caused by its higher charging plateau. Here, a novel “trinity” Li−CO2 battery system was developed by synergizing CO2, soluble redox mediator (2,2,6,6‐tetramethylpiperidoxyl, as TEM RM), and reduced graphene oxide electrode to enable selective conversion of CO2 to Li2C2O4. The designed Li−CO2 battery exhibited an output plateau reaching up to 2.97 V, higher than the equilibrium potential of 2.80 V for Li2CO3, and an ultrahigh round‐trip efficiency of 97.1 %. The superior performance of Li−CO2 batteries is attributed to the TEM RM‐mediated preferential growth mechanism of Li2C2O4, which enhances the reaction kinetics and rechargeability. Such a unique design enables batteries to cope with sudden CO2‐deficient environments, which provides an avenue for the rationally design of CO2 conversion reactions and a feasible guide for next‐generation Li−CO2 batteries.
The “trinity” strategy provides a new perspective for the development of Li−CO2 batteries. The addition of a soluble mediator, TEM RM, was used to modulate the three‐phase interface and facilitate the conversion of CO2 to Li2C2O4. This strategy avoids a series of issues associated with the Li2CO3 product, contributing to excellent cycling performance for Li−CO2 battery.
ENO1 (α-enolase) expression is significantly correlated with reduced survival and poor prognosis in many cancer types, including lung cancer. However, the function of ENO1 in carcinogenesis remains ...elusive. In this study, we found that high expression of ENO1 is present in metastatic lung cancer cell lines and malignant tumors and is associated with poor overall survival of patients with lung cancer. Knockdown of ENO1 decreased cancer cell proliferation and invasiveness, whereas overexpression of ENO1 enhanced these processes. Moreover, ENO1 expression promoted tumor growth in orthotopic models and enhanced lung tumor metastasis in tail-vein injection models. These effects were mediated by upregulation of mesenchymal markers N-cadherin and vimentin and the epithelial-to-mesenchymal transition regulator SLUG, along with concurrent downregulation of E-cadherin. Mechanistically, ENO1 interacted with hepatocyte growth factor receptor (HGFR) and activated HGFR and Wnt signaling via increased phosphorylation of HGFR and the Wnt coreceptor LRP5/6. Activation of these signaling axes decreased GSK3β activity via Src-PI3K-AKT signaling and inactivation of the β-catenin destruction complex to ultimately upregulate SLUG and β-catenin. In addition, we generated a chimeric anti-ENO1 mAb (chENO1-22) that can decrease cancer cell proliferation and invasion. chENO1-22 attenuated cancer cell invasion by inhibiting ENO1-mediated GSK3β inactivation to promote SLUG protein ubiquitination and degradation. Moreover, chENO1-22 prevented lung tumor metastasis and prolonged survival in animal models. Taken together, these findings illuminate the molecular mechanisms underlying the function of ENO1 in lung cancer metastasis and support the therapeutic potential of a novel antibody targeting ENO1 for treating lung cancer. SIGNIFICANCE: This study shows that ENO1 promotes lung cancer metastasis via HGFR and WNT signaling and introduces a novel anti-ENO1 antibody for potential therapeutic use in lung cancer.
Fluid invasion into porous media to displace a more viscous fluid exhibits various displacement patterns. For such unfavorable displacements, previous works overlooked the dynamic effect of viscous ...force on pattern transitions at low flow rates. Consequently, the crossover from compact displacement to capillary fingering under various wetting conditions remains unclear. Here, we establish a theoretical model to capture pattern transitions affected by wettability and flow rate. We rigorously quantify the dynamic effect of viscous force and find that critical contact angles for the crossover from compact displacement to capillary fingering decrease with capillary number. Our model also well describes transitions from capillary fingering to the crossover to viscous fingering. The predicted phase diagram exhibits good agreement with our pore‐scale simulations and microfluidic experiments and is highly consistent with existing experiments. This work extends the classic phase diagram under unfavorable conditions and is of practical significance in subsurface applications.
Plain Language Summary
Fluid invasion into porous media saturated with another more viscous, immiscible fluid exhibits various displacement patterns. The patterns are controlled by the competition between capillary and viscous forces and significantly affect oil recovery and CO2 trapping efficiency. Although invasion patterns have been studied intensively, the dynamic effect of viscous force on pattern transitions is neglected. The crossovers from compact displacement to capillary fingering are not well understood. To explore pattern transitions affected by wettability and flow rate, we perform theoretical analysis of flow behavior at the pore scale, and then establish a model to describe pattern transitions as functions of contact angle and capillary number. We rigorously consider the dynamic effect of viscous force and find that the critical contact angles for the crossover from compact displacement to capillary fingering decrease with capillary number. The model also well describes the crossover from capillary to viscous fingering. We evaluate the phase diagram using pore‐scale simulations, and microfluidic experiments performed in this and previous studies, justifying that the diagram can well capture the transitions under various wetting and flow‐rate conditions. This work extends the classic phase diagram and is also of practical significance in predicting displacement patterns in subsurface applications.
Key Points
We propose a model to describe pattern transitions affected by wettability and flow rate under unfavorable conditions
The model quantifies both the dynamic effect of viscous force and the crossover from compact displacement to capillary fingering
Phase diagram predicted by the model exhibits good agreement with both pore‐scale simulations and microfluidic experiments
Metal borides/borates have been considered promising as oxygen evolution reaction catalysts; however, to date, there is a dearth of evidence of long-term stability at practical current densities. ...Here we report a phase composition modulation approach to fabricate effective borides/borates-based catalysts. We find that metal borides in-situ formed metal borates are responsible for their high activity. This knowledge prompts us to synthesize NiFe-Boride, and to use it as a templating precursor to form an active NiFe-Borate catalyst. This boride-derived oxide catalyzes oxygen evolution with an overpotential of 167 mV at 10 mA/cm
in 1 M KOH electrolyte and requires a record-low overpotential of 460 mV to maintain water splitting performance for over 400 h at current density of 1 A/cm
. We couple the catalyst with CO reduction in an alkaline membrane electrode assembly electrolyser, reporting stable C
H
electrosynthesis at current density 200 mA/cm
for over 80 h.
The association between subclinical hypothyroidism (SCH) and metabolic syndrome (MetS) has been widely discussed. This study aimed to conduct an update and comprehensive meta-analysis to reveal the ...risk of MetS and its components in SCH. PubMed, Embase and ISI Web of Knowledge were searched to identify relevant studies through February 20th, 2020. Review Manager 5.3 and Stata 14.0 were used to conduct the meta-analysis. Both fixed-effects and random-effects models were used. In total, 18 articles (19 studies) incorporating 79,727 participants were included. The pooled OR for MetS comparing subjects with SCH with euthyroid subjects was 1.28 (95% CI: 1.19 to 1.39, p = 0.04, I2 = 40%). Subgroup analysis results showed significant associations of SCH and MetS in the adult subgroup (OR = 1.28, 95% CI: 1.18–1.40), Asian population subgroup (OR = 1.30, 95% CI: 1.19–1.42) and cross-sectional study design subgroup (OR = 1.31, 95% CI: 1.16–1.47). Significant associations of SCH and MetS also existed in all MetS definition criteria subgroups except the Chinese Diabetes Society (CDS) subgroup. SCH was correlated with MetS and was not affected by the subgroup analysis stratified by the proportion of females in the total population, the TSH cutoff value in SCH diagnostic criteria, or the adjustment for confounding factors. SCH was identified to be associated with an increased risk of obesity, hypertension, high triglyceride (TG) levels and low high-density lipoprotein cholesterol (HDL-C) levels. In conclusion, SCH is significantly associated with an increased risk of MetS and four out of five components of MetS.
Based on qualitative and quantitative analyses of the dynamic invasion morphologies, we for the first time proposed a full phase diagram of displacement patterns for rough fracture, showing the ...domains of pattern formations and the displacement efficiency as a function of capillary number Ca and viscous ratio M. The displacement efficiency decreases with Ca in the domain of compact-displacement. We can show that this efficiency reduction is attributed to the onset of localized flow channel induced by the spatial variability of fracture aperture.
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•A phase diagram for immiscible displacement in a rough fracture was proposed.•Displacement efficiency decreases with flow rates under favorable conditions.•The localized flow channel causes earlier breakthrough and reduces the efficiency.
Two-phase flow in fractured media plays an important role in various subsurface processes, including enhanced oil recovery and geological carbon sequestration. The fluid–fluid immiscible displacement patterns range from viscous to capillary fingering to compact displacement owing to the competition between capillary and viscous forces. Although has been profoundly studied for porous media, the phase diagram of displacement patterns as well as the displacement efficiency was rarely reported for rough fractures. Here we studied immiscible displacements in a horizontal transparent rough fracture under a wide range of capillary number Ca and viscosity ratio M. We performed drainage experiments of water-glycerol mixture displacing silicone oil to visualize the displacement processes under favorable conditions (1 ≤ log10M ≤ 3). Based on qualitative and quantitative analyses of the dynamic invasion morphologies, we for the first time proposed a full phase diagram for rough fracture, showing the domains of pattern formations (viscous fingering, capillary fingering and compact displacement) and the corresponding displacement efficiency as a function of Ca and M. The phase diagram indicates that the displacement efficiency decreases with the increase of Ca in the domain of compact-displacement. We can show that this efficiency reduction is attributed to the onset of localized flow channel induced by the spatial variability of fracture aperture. In this zone, the front is stable at initial stage until approaching a critical location, after which a finger is initiated and advances toward the outlet along the center of the fracture void space with much higher velocity, demonstrating the important role of the heterogeneity of fracture geometry in the displacement processes. This study not only extends the phase diagram from porous media to rough fractures but also improves our understanding of the dynamics of displacement processes jointly governed by the viscous/capillary forces and the fracture geometry under favorable conditions.
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