scholarly journals Roles of vertical distributions of atmospheric transient eddy dynamical forcing and diabatic heating in midlatitude unstable air–sea interaction

2021 ◽  
Author(s):  
Jiabei Fang ◽  
Lilan Chen ◽  
Xiu-Qun Yang
Keyword(s):  
Positive Feedback ◽  
Diabatic Heating ◽  
Lower Layer ◽  
Theoretical Work ◽  
Atmospheric Model ◽  
Feedback Mechanism ◽  
Transient Eddy ◽  
Coupled Mode ◽  
Vertical Distributions ◽  
Positive Feedback Mechanism

AbstractAtmospheric transient eddy dynamical forcing (TEDF)-driven midlatitude unstable air–sea interaction has recently been recognized as a crucial positive feedback for the maintenance of the extratropical decadal variabilities. Our recent theoretical work (Chen et al., Clim Dyn 10.1007/s00382-020-05405-0, 2020) has characterized such an interaction through building an analytical midlatitude barotropic atmospheric model coupled to a simplified upper oceanic model. This study extends the analytical model to including a two-layer quasi-geostrophic baroclinic atmospheric model and then identifies the roles of vertical distributions of atmospheric TEDF and diabatic heating in midlatitude unstable air–sea interaction. It is found that midlatitude air–sea coupling with more realistic vertical profiles of atmospheric TEDF and diabatic heating destabilizes oceanic Rossby wave modes over the entire range of zonal wavelengths, in which the most unstable coupled mode features an equivalent barotropic atmospheric low (high) pressure over a cold (warm) oceanic surface. Spatial structure and period of the most unstable mode are more consistent with the observation than those from in previous model. Although either TEDF or diabatic heating alone can lead to a destabilized coupled mode, the former makes a dominant contribution to the instability. The increase of low-layer TEDF stimulates the instability more effectively if the TEDF in upper layer is larger than in lower layer, while the TEDF in either high or low layers can individually cause the instability. The surface heating always destabilizes the air–sea interaction, while the mid-level heating always decays the coupled mode. The results of this study further confirm the TEDF-driven positive feedback mechanism in midlatitude air–sea interaction proposed by recent observational and numerical experiment studies.

scholarly journals Roles of vertical distributions of atmospheric transient eddy dynamical forcing and diabatic heating in midlatitude unstable air-sea interaction

2021 ◽  
Author(s):  
Jiabei Fang ◽  
Lilan Chen ◽  
Xiu-Qun Yang
Keyword(s):  
Positive Feedback ◽  
Diabatic Heating ◽  
Spatial Configuration ◽  
Lower Layer ◽  
Theoretical Work ◽  
Atmospheric Model ◽  
Transient Eddy ◽  
Coupled Mode ◽  
Vertical Distributions ◽  
Oceanic Model

Abstract Atmospheric transient eddy dynamical forcing (TEDF)-driven midlatitude unstable air-sea interaction has recently been recognized as a crucial positive feedback for the maintenance of the extratropical decadal variabilities. Our previous theoretical work by Chen et al. (2020) characterizes such an interaction with building an analytical midlatitude barotropic atmospheric model coupled to a simplified upper oceanic model. This study firstly extends the analytical model to a two-layer quasi-geostrophic baroclinic atmospheric model coupled to a simplified upper oceanic model and then identifies the roles of vertical distributions of atmospheric TEDF and diabatic heating in midlatitude unstable air-sea interaction. It is found that the midlatitude air-sea coupling through atmospheric TEDF and diabatic heating with more realistic vertical profile destabilizes the oceanic Rossby wave mode over the entire range of zonal wavelengths, and the most unstable mode exhibits an equivalent barotropic structure with geopotential lows (highs) over cold (warm) water. The spatial configuration structure and period of the most unstable coupled mode are more consistent with the observation than those from the previous model. Although either TEDF or diabatic heating alone can lead to unstable air-sea interaction, the former is dominant to the instability. TEDF in both higher and lower layers can cause unstable coupled mode individually, while the lower-layer forcing stimulates instability more effectively. Surface diabatic heating always destabilizes the coupled mode, while the mid-level heating always decays the coupled mode. Moreover, the influences of oceanic adjustment processes, air-sea coupling strength and background zonal wind on the unstable coupled mode are also discussed. The results of this study further prove the TEDF-driven positive feedback mechanism in midlatitude air-sea interaction proposed by recent observational and numerical experiment studies.

Analysis of a positive feedback mechanism in the anti-Sm autoantibody response of MRL/MPJ-lpr/lpr mice

1991 ◽  
Vol 21 (2) ◽  
pp. 267-272 ◽  
Author(s):  
Martin Robert Stocks ◽  
David Gareth Williams ◽  
Ravinder Nath Maini
Keyword(s):  
Positive Feedback ◽  
Feedback Mechanism ◽  
Autoantibody Response ◽  
Positive Feedback Mechanism

scholarly journals A positive feedback mechanism ensures proper assembly of the functional inner centromere during mitosis in human cells

2018 ◽  
Vol 294 (5) ◽  
pp. 1437-1450 ◽  
Author(s):  
Cai Liang ◽  
Zhenlei Zhang ◽  
Qinfu Chen ◽  
Haiyan Yan ◽  
Miao Zhang ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Histone H3 ◽  
Causal Link ◽  
Feedback Mechanism ◽  
Histone H2a ◽  
Defective Mutant ◽  
Chromosomal Passenger ◽  
Phosphatase 2A ◽  
Elevated Rate ◽  
Positive Feedback Mechanism

The inner centromere region of a mitotic chromosome critically regulates sister chromatid cohesion and kinetochore–microtubule attachments. However, the molecular mechanism underlying inner centromere assembly remains elusive. Here, using CRISPR/Cas9-based gene editing in HeLa cells, we disrupted the interaction of Shugoshin 1 (Sgo1) with histone H2A phosphorylated on Thr-120 (H2ApT120) to selectively release Sgo1 from mitotic centromeres. Interestingly, cells expressing the H2ApT120-binding defective mutant of Sgo1 have an elevated rate of chromosome missegregation accompanied by weakened centromeric cohesion and decreased centromere accumulation of the chromosomal passenger complex (CPC), an integral part of the inner centromere and a key player in the correction of erroneous kinetochore–microtubule attachments. When artificially tethered to centromeres, a Sgo1 mutant defective in binding protein phosphatase 2A (PP2A) is not able to support proper centromeric cohesion and CPC accumulation, indicating that the Sgo1–PP2A interaction is essential for the integrity of mitotic centromeres. We further provide evidence indicating that Sgo1 protects centromeric cohesin to create a binding site for the histone H3–associated protein kinase Haspin, which not only inhibits the cohesin release factor Wapl and thereby strengthens centromeric cohesion but also phosphorylates histone H3 at Thr-3 to position CPC at inner centromeres. Taken together, our findings reveal a positive feedback–based mechanism that ensures proper assembly of the functional inner centromere during mitosis. They further suggest a causal link between centromeric cohesion defects and chromosomal instability in cancer cells.

scholarly journals Hedgehog signaling activates a positive feedback mechanism involving insulin-like growth factors to induce osteoblast differentiation

2015 ◽  
Vol 112 (15) ◽  
pp. 4678-4683 ◽  
Author(s):  
Yu Shi ◽  
Jianquan Chen ◽  
Courtney M. Karner ◽  
Fanxin Long
Keyword(s):  
Transcriptional Activation ◽  
Positive Feedback ◽  
Hedgehog Signaling ◽  
Osteoblast Differentiation ◽  
Akt Signaling ◽  
Feedback Mechanism ◽  
Genetic Deletion ◽  
Positive Feedback Mechanism ◽  
Igf Signaling

Hedgehog (Hh) signaling is essential for osteoblast differentiation in the endochondral skeleton during embryogenesis. However, the molecular mechanism underlying the osteoblastogenic role of Hh is not completely understood. Here, we report that Hh markedly induces the expression of insulin-like growth factor 2 (Igf2) that activates the mTORC2-Akt signaling cascade during osteoblast differentiation. Igf2-Akt signaling, in turn, stabilizes full-length Gli2 through Serine 230, thus enhancing the output of transcriptional activation by Hh. Importantly, genetic deletion of the Igf signaling receptor Igf1r specifically in Hh-responding cells diminishes bone formation in the mouse embryo. Thus, Hh engages Igf signaling in a positive feedback mechanism to activate the osteogenic program.

scholarly journals Survival and Proliferation of Neural Progenitor–Derived Glioblastomas Under Hypoxic Stress is Controlled by a CXCL12/CXCR4 Autocrine-Positive Feedback Mechanism

2016 ◽  
Vol 23 (5) ◽  
pp. 1250-1262 ◽  
Author(s):  
Anda-Alexandra Calinescu ◽  
Viveka Nand Yadav ◽  
Erica Carballo ◽  
Padma Kadiyala ◽  
Dustin Tran ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Neural Progenitor ◽  
Feedback Mechanism ◽  
Hypoxic Stress ◽  
Positive Feedback Mechanism

Inverter design with positive feedback field-effect transistors

2021 ◽  
Author(s):  
Changhoon Lee ◽  
Changwoo Han ◽  
Changhwan Shin
Keyword(s):  
Positive Feedback ◽  
Computer Aided Design ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Feedback Mechanism ◽  
Silicon On Insulator ◽  
Logic Device ◽  
Device Applications ◽  
Positive Feedback Mechanism ◽  
Switching Devices

Abstract As the physical size of semiconductor devices continues to be aggressively scaled down, feedback field-effect transistors (FBFET) with a positive feedback mechanism among a few promising steep switching devices have received attention as next-generation switching devices. Conventional FBFETs have been studied to explore their device performance. However, this has been restricted to the case of single FBFET; basic circuit designs with FBFETs have not been investigated extensively. In this work, we propose an inverter circuit design with silicon-on-insulator (SOI) FBFETs; we verified this inverter design with mixed-mode technology computer-aided design simulation. The basic principles and mechanisms for designing FBFET inverter circuits are explained because their configuration is different from conventional inverters. In addition, the device parameters necessary to optimize circuit construction are introduced for logic device applications.

scholarly journals A Positive Feedback Mechanism of Adaptive Dynamic System

2019 ◽  
Vol 569 ◽  
pp. 042009
Author(s):  
Pengchao Wang ◽  
Fucai Chen ◽  
Guozhen Cheng
Keyword(s):  
Dynamic System ◽  
Positive Feedback ◽  
Feedback Mechanism ◽  
Adaptive Dynamic ◽  
Positive Feedback Mechanism
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