Peter Liu

Carleton University

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Co-Authors

Huanqing Wang

Bohai University

Robert O. Bonow

Northwestern University

Myron L. Weisfeldt

Johns Hopkins Medicine

Patrick T. O’Gara

Harvard University

Marc S. Sabatine

Thrombolysis in Myocardial Infarction Study Group

New York

Princeton Public Schools

Renato D. Lópes

Clinical Research Institute

Michael Pencina

Duke University

Karen Bucher

International Rescue Committee

Hugh Watkins

University of Oxford

Cooperative Institutions

Advisory Board Company (United States)

850

Palo Alto Institute

847

Tokyo Institute of Technology

606

IT University of Copenhagen

601

Administration for Community Living

597

American Jewish Committee

562

University of Toronto

399

University of Washington

313

RIKEN Center for Advanced Intelligence Project

296

Mongolia International University

283

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UBR E3 ligases and the PDIA3 protease control degradation of unfolded antibody heavy chain by ERAD

The Journal of Cell Biology (2020)

Danming Tang Wendy Sandoval Cynthia Lam Benjamin Haley Peter Liu

Accumulation of unfolded antibody chains in the ER triggers ER stress that may lead to reduced productivity in therapeutic antibody manufacturing processes. We identified UBR4 and UBR5 as ubiquitin E3 ligases involved in HC ER-associated degradation. Knockdown of UBR4 and UBR5 resulted in intracellular accumulation, enhanced secretion, and reduced ubiquitination of HC. In concert with these E3 ligases, PDIA3 was shown to cleave ubiquitinated HC molecules to accelerate HC dislocation. Interestingly, UBR5, and to a lesser degree UBR4, were down-regulated as cellular demand for antibody expression increased in CHO cells during the production phase, or in plasma B cells. Reducing UBR4/UBR5 expression before the production phase increased antibody productivity in CHO cells, possibly by redirecting antibody molecules from degradation to secretion. Altogether we have characterized a novel proteolysis/proteasome-dependent pathway involved in degradation of unfolded antibody HC. Proteins characterized in this pathway may be novel targets for CHO cell engineering.

Endoplasmic-reticulum-associated protein degradation

Proteolysis

10.1083/jcb.201908087

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Citations (9)

Feasibility Analysis of Localized SOI Platform Detection Method Based on Carrier Grating

Peter Liu Jinze Shi Changying Li Qing Wang Jiajun Wan

As the quantity and variety of devices integrated into Silicon-on-Insulator(SOI) platform continue to escalate, it becomes increasingly challenging to determine the modes' behavior on the positions of concern relying solely on pre-processed couplers. Interference of two coherent pump beams has the capability to induce a periodic carrier distribution in the material, thus modulating the refractive index, effectively creating a temporary and erasable diffraction grating. In this study, an off-chip, non-destructive and localized detection method based on carrier grating is proposed. A theoretical model is developed to calculate carrier dynamics under various pump configurations. Leveraging the Finite-Difference Time-Domain (FDTD) method and accounting for Free Carrier Index (FCI) and Free Carrier Absorption (FCA) effects, analysis of the quantitative impact of pump intensity and radius on the diffraction efficiency of the carrier grating in Silicon-on-Insulator (SOI) Platform and its far-field divergence characteristics are provided. Ultimately, this research contributes to a discussion on the feasibility of experimental approaches with a spatial resolution of less than 10 μm, -15 dB diffraction efficiency, simultaneously maintaining a far-field divergence of 7.8° for SOI platform.

Diffraction efficiency

10.1364/opticaopen.25009715.v1

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Citations (0)

When the Smart Grid Meets Energy-Efficient Communications: Green Wireless Cellular Networks Powered by the Smart Grid

IEEE Transactions on Wireless Communications (2012)

Shengrong Bu F. Richard Yu Mark Yep-Kui Chua Peter Liu

Recently, there is great interest in considering the energy efficiency aspect of cellular networks. On the other hand, the power grid infrastructure, which provides electricity to cellular networks, is experiencing a significant shift from the traditional electricity grid to the smart grid. When a cellular network is powered by the smart grid, only considering energy efficiency in the cellular network may not be enough. In this paper, we consider not only energy-efficient communications but also the dynamics of the smart grid in designing green wireless cellular networks. Specifically, the dynamic operation of cellular base stations depends on the traffic, real-time electricity price, and the pollutant level associated with electricity generation. Coordinated multipoint (CoMP) is used to ensure acceptable service quality in the cells whose base stations have been shut down. The active base stations decide on which retailers to procure electricity from and how much electricity to procure. We formulate the system as a Stackelberg game, which has two levels: a cellular network level and a smart grid level. Simulation results show that the smart grid has significant impacts on green wireless cellular networks, and our proposed scheme can significantly reduce operational expenditure and CO_2 emissions in green wireless cellular networks.

Base transceiver station

10.1109/twc.2012.052512.111766

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Citations (225)

Parameter estimation with scarce measurements

Automatica (2011)

Feng Ding Guangjun Liu Peter Liu

Lemma (botany)

Representation

10.1016/j.automatica.2011.05.007

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Citations (256)

Particle filtering enhanced human tracking on context-aware robotic system

Kun Wang Peter Liu

This paper presents the mechanism of visual tracking implemented on a context-aware robotic platform with layered and centralized system architecture. The visual tracking mechanism is developed using Haar-like feature detection algorithm, enhanced by modified Particle Filtering (PF) method, to realize human face tracking and following on a mobile robot platform. Experimental results demonstrate the feasibility and effectiveness of the proposed implementation of visual contexts on the context-aware robotic system.

Tracking (education)

Feature (linguistics)

Tracking system

10.1109/have.2013.6679617

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Citations (3)

Elafin-overexpressing mice have improved cardiac function after myocardial infarction

AJP Heart and Circulatory Physiology (2004)

Kunio Ohta Takanori Nakajima Alexander Y. L. Cheah Syed Hassan Ejaz Zaidi Nilo Kaviani

Elevated serine elastase activity after myocardial infarction can contribute to remodeling associated with left ventricular dilatation and dysfunction. We therefore assessed the effects of overexpressing the selective serine elastase inhibitor elafin in transgenic mice in which a myocardial infarction was caused by ligation of the left anterior descending coronary artery (LAD). Elevated serine elastase activity was observed in nontransgenic littermates as early as 6 h after LAD ligation and persisted at 4 and 7 days but not in sham-operated or elafin-overexpressing transgenic mice. Myeloperoxidase activity (index of inflammatory cells) and matrix metalloproteinase 2 were also increased but only at 4 and 7 days and only in nontransgenic mice (P < 0.05 for both comparisons), and this increase correlated with inflammatory cell infiltration. Echocardiographic study at 4 days revealed indexes of diastolic dysfunction in nontransgenic versus elafin-overexpressing mice (P < 0.05). Morphometric and biochemical analyses at 28 days indicated impairment in cardiac performance, with greater scar thinning and infarct expansion in nontransgenic versus elafin transgenic littermates (P < 0.05 for all comparisons). Thus serine elastase inhibition appears to suppress inflammation, cardiac dilatation, and dysfunction after myocardial infarct.

Elafin

Neutrophil elastase

10.1152/ajpheart.00479.2002

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Citations (43)

Aerobic capacity in adults with tetralogy of Fallot

Cardiology in the Young (2002)

Per Morten Fredriksen Judith Therrien Gruschen Veldtman Mohammed Ali Warsi Peter Liu

Background: We investigated the aerobic capacity of 168 adult patients who had undergone successful surgical repair of tetralogy of Fallot at the University of Toronto Congenital Cardiac Centre for Adults. Methods: We compared values of peak uptake of oxygen, peak heart rate, forced vital capacity, and forced expiratory volume in 1 second to predicted values for their age groups. Results: The patients who had undergone surgical repair of tetralogy of Fallot demonstrated an overall diminished peak uptake of oxygen, at 51%, and peak heart rate, at 79%, compared to predicted values. No difference in peak aerobic capacity was found according to the initial surgical strategy of palliation or repair. Conclusions: Adult patients who have undergone surgical repair of tetralogy of Fallot have lower peak uptake of oxygen, and peak heart rate, compared to predicted values. The reduction in the peak heart rate may affect their exercise capacity. The peak uptake of oxygen also decreased with increasing age at the time of testing, and the age at surgical repair.

Aerobic capacity

Vital capacity

10.1017/s1047951102001002

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Citations (60)

On the model-based approach to nonlinear networked control systems

Automatica (2008)

Ilia G. Polushin Peter Liu Chung‐Horng Lung

Feed forward

Networked control system

10.1016/j.automatica.2008.01.031

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Citations (103)

Adaptive control for nonlinear time-delay systems with low triangular structure

Guangwei Li Chuangzhi Zang Peter Liu

Adaptive control of nonlinear time-delay system with low triangular structure is considered in this paper. Based on Lyapunov stability theory and Lyapunov-Krasovskii functional, an adaptive controller was proposed by the backstepping technique and parameter estimation method. The adaptive controller can make the closed-loop system uniformly asymptotically stable.

Stability theory

Strict-feedback form

Lyapunov stability

Adaptive system

10.23919/acc.2004.1383670

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Citations (3)

An Improved Level Set Method for Reachability Problems in Differential Games

IEEE Transactions on Systems Man and Cybernetics Systems (2024)

Wei Liao Taotao Liang Pengwen Xiong Chen Wang Aiguo Song

This study focuses on reachability problems in differential games. An improved level set (LS) method for computing reachable tubes (RTs) is proposed in this article. The RT is described as a sub-LS of a value function, which is the viscosity solution of a Hamilton–Jacobi (HJ) equation with running cost. We generalize the concept of RTs and propose a new class of RTs, which are referred to as cost-limited one. In particular, a performance index can be specified for the system, and A set of initial states of the system’s evolutions that can reach the target set before the performance index grows to a given allowable cost is referred to as a cost-limited RT (CRT). Such an RT can be obtained by specifying the corresponding running cost function for the HJ equation. Different nonzero sub-LSs of the viscosity solution of the HJ equation at a certain time point can be used to characterize the CRTs with different allowable costs (or the RTs with different time horizons), thus reducing the storage space consumption. The validity and accuracy of the suggested technique are demonstrated via some examples.

10.1109/tsmc.2024.3352263

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Citations (1)