Necessary and sufficient conditions for oscillations of delay equations with impulses

AbstractIn this paper, a necessary and sufficient condition for oscillation of a first-order delay differential equation with impulses x′(t)+∑i=1npix(t−τi)=0, t≠tk,x(tk+)−x(tk=bkx(tk), k=1,2,… is established

Oscillation properties of nonlinear impulsive delay differential equations and applications to population models

AbstractComparison theorem and explicit sufficient conditions are obtained for oscillation and nonoscillation of solutions of nonlinear impulsive delay differential equations which can be utilized to population dynamic models. Our results in this paper generalize and improve several known results

Double-Stranded RNA-Dependent Protein Kinase (PKR) is Downregulated by Phorbol Ester

The double-stranded RNA-dependent protein kinase (PKR) is one of the key mediators of interferon (IFN) action against certain viruses. PKR also plays an important role in signal transduction and immunomodulation. Understanding the regulation of PKR activity is important for the use of PKR as a tool to discover and develop novel therapeutics for viral infections, cancer and immune dysfunction. We found that phorbol 12-myristate 13-acetate (PMA), a potent activator of protein kinase C (PKC), decreased the level of autophosphorylated PKR in a dose- and time-dependent manner in IFN-treated mouse fibroblast cells. Polyinosinic–polycytidylic acid (poly I:C) treatment enhanced the activity of PKR induced by IFN, but did not overcome the PMA-induced reduction of PKR autophosphorylation. Western blot analysis with a monoclonal antibody to mouse PKR revealed that the decrease of PKR autophosphorylation in cells by PMA was a result of PKR protein degradation. Selective PKC inhibitors blocked the degradation of PKR stimulated by PMA, indicating that PKC activity was required for the effect. Furthermore, we also found that proteasome inhibitors prevented PMA-induced down regulation of PKR, indicating that an active proteasome is required. Our results identify a novel mechanism for the post-translational regulation of PKR

Distinct features of nucleolus-associated domains in mouse embryonic stem cells [preprint]

Background Heterochromatin in eukaryotic interphase cells frequently localizes to the nucleolar periphery (nucleolus-associated domains, NADs) and the nuclear lamina (lamina-associated domains, LADs). Gene expression in somatic cell NADs is generally low, but NADs have not been characterized in mammalian stem cells. Results Here, we generated the first genome-wide map of NADs in mouse embryonic stem cells (mESCs) via deep sequencing of chromatin associated with biochemically-purified nucleoli. As we had observed in mouse embryonic fibroblasts (MEFs), the large Type I subset of NADs overlaps with constitutive LADs and is enriched for features of constitutive heterochromatin, including late replication timing and low gene density and expression levels. Conversely, the Type II NAD subset overlaps with loci that are not lamina-associated, but in mESCs, Type II NADs are much less abundant than in MEFs. mESC NADs are also much less enriched in H3K27me3 modified regions than are NADs in MEFs. Additionally, comparision of MEF and mESC NADs revealed enrichment of developmentally regulated genes in cell type-specific NADs. Together, these data indicate that NADs are a developmentally dynamic component of heterochromatin. Conclusions These studies implicate association with the nucleolar periphery as a mechanism for developmentally-regulated gene silencing, and will facilitate future studies of NADs during mESC differentiation

BP Neural Network Algorithms for Fault Diagnosis of Microwave Components

Intelligent diagnosis is the main trend of modern fault diagnosis technology. The emergence of artificial neural network technology provides a new way for this kind of intellectualization. Aiming at the problem of microwave module fault diagnosis, an intelligent fault diagnosis method based on BP(Back Propagation) neural network is proposed in this paper. In this paper, the process of determining the neural network model and the operation flow of BP algorithm are introduced, and the network is trained with training samples. By applying the neural network model to an AQ module for testing, the feasibility, accuracy and efficiency of the fault diagnosis of the microwave module are verified, which provides a new method for intelligent fault diagnosis of this kind of microwave module

Double-Stranded RNA-Dependent Protein Kinase (PKR) is Downregulated by Phorbol Ester

The double-stranded RNA-dependent protein kinase (PKR) is one of the key mediators of interferon (IFN) action against certain viruses. PKR also plays an important role in signal transduction and immunomodulation. Understanding the regulation of PKR activity is important for the use of PKR as a tool to discover and develop novel therapeutics for viral infections, cancer and immune dysfunction. We found that phorbol 12-myristate 13-acetate (PMA), a potent activator of protein kinase C (PKC), decreased the level of autophosphorylated PKR in a dose- and time-dependent manner in IFN-treated mouse fibroblast cells. Polyinosinic–polycytidylic acid (poly I:C) treatment enhanced the activity of PKR induced by IFN, but did not overcome the PMA-induced reduction of PKR autophosphorylation. Western blot analysis with a monoclonal antibody to mouse PKR revealed that the decrease of PKR autophosphorylation in cells by PMA was a result of PKR protein degradation. Selective PKC inhibitors blocked the degradation of PKR stimulated by PMA, indicating that PKC activity was required for the effect. Furthermore, we also found that proteasome inhibitors prevented PMA-induced down regulation of PKR, indicating that an active proteasome is required. Our results identify a novel mechanism for the post-translational regulation of PKR