4,784 research outputs found
Nilpotent center conditions in cubic switching polynomial Li\'enard systems by higher-order analysis
The aim of this paper is to investigate two classical problems related to
nilpotent center conditions and bifurcation of limit cycles in switching
polynomial systems. Due to the difficulty in calculating the Lyapunov constants
of switching polynomial systems at non-elementary singular points, it is
extremely difficult to use the existing Poincar\'e-Lyapunov method to study
these two problems. In this paper, we develop a higher-order
Poincar\'e-Lyapunov method to consider the nilpotent center problem in
switching polynomial systems, with particular attention focused on cubic
switching Li\'enard systems. With proper perturbations, explicit center
conditions are derived for switching Li\'enard systems at a nilpotent center,
which is characterized as global. Moreover, with Bogdanov-Takens bifurcation
theory, the existence of five limit cycles around the nilpotent center is
proved for a class of switching Li\'enard systems, which is a new lower bound
of cyclicity for such polynomial systems around a nilpotent center
The Possibility of Mirror Planet as Planet Nine in Solar System
A series of dynamical anomalies in the orbits of distant trans-Neptunian
objects points to a new celestial body (usually named Planet Nine) in the solar
system. In this draft, we point out that a mirror planet captured from the
outer solar system or formed in the solar system is also a possible candidate.
The introduction of the mirror matter model is due to an unbroken parity
symmetry and is a potential explanation for dark matter. This mirror planet has
null or fainter electromagnetic counterparts with a smaller optical radius and
might be explored through gravitational effects
A Multisampling Reporter System for Monitoring MicroRNA Activity in the Same Population of Cells
MicroRNAs (miRNAs) downregulate gene expression by binding to the partially complementary sites in the 3′ untranslated region (UTR) of target mRNAs. Several methods, such as Northern blot analysis, quantitative real-time RT-PCR, microarray, and the luciferase reporter system, are commonly used to quantify the relative level or activity of miRNAs. The disadvantage of these methods is the requirement for cell lysis, which means that several sets of wells/dishes of cells must be prepared to monitor changes in miRNA activity in time-course studies. In this study, we developed a multisampling reporter system in which two secretable bioluminescence-generating enzymes are employed, one as a reporter and the other as an internal control. The reporters consist of a pair of vectors containing the Metridia luciferase gene, one with and one without a duplicated miRNA targeting sequence at their 3′UTR, while the other vector coding for the secreted alkaline phosphatase gene is used as an internal control. This method allows miRNA activity to be monitored within the same population of cells over time by withdrawing aliquots of the culture medium. The practicability and benefits of this system are addressed in this report
Designing Public Innovations in Public Sector: The Process and Challenges in Taiwanese E-government
Researchers have found that a one-sided focus on technology dominates many e-government projects; ICT has been used mainly as a tool to enhance the efficiency and service delivery of the government. In fact, e-government should achieve public innovation goals, such as redesigning information relationships among stakeholders, enhancing citizen participation in the policymaking process, and reinforcing policy enforcement to create public value. These goals are more valuable, but also more complex than the digitization of existing governmental processes. Beside, only a few projects could achieve the public innovation diffusion goal among many e-government projects. Therefore, this case study focuses on a very important and successful e-government project in Taiwan – the e-invoicing project, by following the development timeline of this 12-year project to understand the reasons of loosing focus and the turning points to achieve the final success. With the results of this case study, this research address four main factors of success in public innovation diffusion: (a) cooperate with the right stakeholder: e-government projects requires intensive cooperation with both public and private organizations, otherwise the change agency has no complete control over its innovation offering; (b) the selection of the right diffusion mode: centralized innovation-diffusion is difficult to overcome the stereotyped perception that citizens hold toward the government, and thus, it is better to implement by a decentralized fashion; (c) the diversity of services: public innovations have an inherently higher complexity than commercial innovations because they intend to serve a diversity of citizens; and (d) assignment of the right change agent for the project: because the burden on the change agent is tremendous, only a few “policy entrepreneurs” can push through the innovation process, despite few material rewards
How tyramine β-hydroxylase controls the production of octopamine, modulating the mobility of beetles
Biogenic amines perform many kinds of important physiological functions in the central nervous system (CNS) of insects, acting as neuromodulators, neurotransmitters, and neurohormones. The five most abundant types of biogenic amines in invertebrates are dopamine, histamine, serotonin, tyramine, and octopamine (OA). However, in beetles, an important group of model and pest insects, the role of tyramine beta-hydroxylase (T beta H) in the OA biosynthesis pathway and the regulation of behavior remains unknown so far. We therefore investigated the molecular characterization and spatiotemporal expression profiles of T beta H in red flour beetles (Triboliun castaneum). Most importantly, we detected the production of OA and measured the crawling speed of beetles after dsTcT beta H injection. We concluded that TcT beta H controls the biosynthesis amount of OA in the CNS, and this in turn modulates the mobility of the beetles. Our new results provided basic information about the key genes in the OA biosynthesis pathway of the beetles, and expanded our knowledge on the physiological functions of OA in insects
Global-Local Stepwise Generative Network for Ultra High-Resolution Image Restoration
While the research on image background restoration from regular size of
degraded images has achieved remarkable progress, restoring ultra
high-resolution (e.g., 4K) images remains an extremely challenging task due to
the explosion of computational complexity and memory usage, as well as the
deficiency of annotated data. In this paper we present a novel model for ultra
high-resolution image restoration, referred to as the Global-Local Stepwise
Generative Network (GLSGN), which employs a stepwise restoring strategy
involving four restoring pathways: three local pathways and one global pathway.
The local pathways focus on conducting image restoration in a fine-grained
manner over local but high-resolution image patches, while the global pathway
performs image restoration coarsely on the scale-down but intact image to
provide cues for the local pathways in a global view including semantics and
noise patterns. To smooth the mutual collaboration between these four pathways,
our GLSGN is designed to ensure the inter-pathway consistency in four aspects
in terms of low-level content, perceptual attention, restoring intensity and
high-level semantics, respectively. As another major contribution of this work,
we also introduce the first ultra high-resolution dataset to date for both
reflection removal and rain streak removal, comprising 4,670 real-world and
synthetic images. Extensive experiments across three typical tasks for image
background restoration, including image reflection removal, image rain streak
removal and image dehazing, show that our GLSGN consistently outperforms
state-of-the-art methods.Comment: submmitted to Transactions on Image Processin
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