Elimination of the numerical Cerenkov instability for spectral EM-PIC codes

When using an electromagnetic particle-in-cell (EM-PIC) code to simulate a relativistically drifting plasma, a violent numerical instability known as the numerical Cerenkov instability (NCI) occurs. The NCI is due to the unphysical coupling of electromagnetic waves on a grid to wave-particle resonances, including aliased resonances, i.e., $\omega + 2\pi\mu/\Delta t=(k_1+ 2\pi\nu_1/\Delta x_1)v_0$, where $\mu$ and $\nu_1$ refer to the time and space aliases and the plasma is drifting relativistically at velocity $v_0$ in the $\hat{1}$-direction. Recent studies have shown that an EM-PIC code which uses a spectral field solver and a low pass filter can eliminate the fastest growing modes of the NCI. Based on these studies a new spectral PIC code for studying laser wakefield acceleration (LWFA) in the Lorentz boosted frame was developed. However, we show that for parameters of relevance for LWFA simulations in the boosted frame, a relativistically drifting plasma is susceptible to a host of additional unstable modes with lower growth rates, and that these modes appear when the fastest growing unstable modes are filtered out. We show that these modes are most easily identified as the coupling between modes which are purely transverse (EM) and purely longitudinal (Langmuir) in the rest frame of the plasma for specific time and space aliases. We rewrite the dispersion relation of the drifting plasma for a general field solver and obtain analytic expressions for the location and growth rate for each unstable mode, i.e, for each time and space aliased resonances. We show for the spectral solver that when the fastest growing mode is eliminated a new mode at the fundamental resonance ($\mu=\nu_1=0$) can be seen. (Please check the whole abstract in the paper).Comment: 36 pages, 12 figure

Adaptive Routing Forwarding Strategy Based on Neural Network Algorithm

With the profound changes in global digital media, the focus of Internet users has gradually shifted to how to quickly obtain information without paying attention to where the information is stored. However, the current TCP/IP network protocol architecture cannot adapt to the rapid development of today#39s content applications. In order to adapt to the changes in the Internet, information-centric networking (ICN)has received extensive attention. Besides, the optimization of the user service request scheduling problem is the core issue affecting the performance of the ICN , and it is one of the hot research topics in the ICN network. To solve this problem, this paper proposes an adaptive routing forwarding strategy based on neural network algorithm. Through the modeling of the classic architecture named data networking (NDN) network delay model of ICN network, a neural network algorithm is used to delay prediction, and a forwarding strategy mechanism based on predict delay is designed to innovate in the NDN. The interface information Stat is added to the forwarding information base (FIB) of the network component to implement the dynamic selection of the forwarding routing. In addition, routing dynamic self-adaptation adjustment mechanism and fault rerouting function are designed in consideration of the situation of route congestion and interruption. Simulation results show that this strategy effectively reduces network delay and improves network performance

Generation of Phenylpropanoid Pathway-Derived Volatiles in Transgenic Plants: Rose Alcohol Acetyltransferase Produces Phenylethyl Acetate and Benzyl Acetate in Petunia Flowers

Esters are important contributors to the aroma of numerous flowers and fruits. Acetate esters such as geranyl acetate, phenylethyl acetate and benzyl acetate are generated as a result of the action of alcohol acetyltransferases (AATs). Numerous homologous AATs from various plants have been characterized using in-vitro assays. To study the function of rose alcohol acetyltransferase (RhAAT) in planta , we generated transgenic petunia plants expressing the rose gene under the control of a CaMV-35S promoter. Although the preferred substrate of RhAAT in vitro is geraniol, in transgenic petunia flowers, it used phenylethyl alcohol and benzyl alcohol to produce the corresponding acetate esters, not generated by control flowers. The level of benzyl alcohol emitted by the flowers of different transgenic lines was ca. three times higher than that of phenylethyl alcohol, which corresponded to the ratio between the respective products, i.e. ca. three times more benzyl acetate than phenylethyl acetate. Feeding of transgenic petunia tissues with geraniol or octanol led to the production of their respective acetates, suggesting the dependence of volatile production on substrate availability.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43457/1/11103_2005_Article_4924.pd

Renal interstitial fibrosis induced by high-dose mesoporous silica nanoparticles via the NF-κB signaling pathway

Xi Chen,1,2 Wang Zhouhua,1 Zhou Jie,1 Fu Xinlu,3 Liang Jinqiang,3 Qiu Yuwen,3 Huang Zhiying1,31School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, People’s Republic of China; 2Pharmaceutical Department, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, People’s Republic of China; 3Center of Laboratory Animals, Sun Yat-sen University, Guangzhou, People’s Republic of China Abstract: Previous studies have indicated that the nephrotoxicity induced by mesoporous silica nanoparticles (MSNs) is closely related to inflammation. Nuclear factor kappa B (NF-κB), a common rapid transcription factor associated with inflammation, plays an important role in the process of many kidney diseases. Acute toxicity assessment with a high-dose exposure is critical for the development of nanoparticle, as a part of standardized procedures for the evaluation of their toxicity. The present study was undertaken to observe the acute toxicity, predict the potential target organs of MSNs injury, and test the hypothesis that the NF-κB pathway plays a role in mediating the acute kidney injury and renal interstitial fibrosis in mice induced by MSNs. Balb/c mice were intraperitoneally injected with MSNs at concentrations of 150, 300, or 600 mg/kg. All of the animals were euthanized 2 and 12 days after exposure, and the blood and kidney tissues were collected for further studies. In vitro, the cytotoxicity, fibrosis markers, and NF-κB pathway were measured in a normal rat kidney cell line (NRK-52E). Acute kidney injury was induced by MSNs in mice after 2 days, some renal tubules regenerated and renal interstitial fibrosis was also observed. The expression of fibrosis markers and the nuclear translocation of NF-κB p65 in the kidney homogenates increased after exposure to MSNs. The in vitro study showed that MSNs cause cytotoxicity in NRK-52E cells and increased the expression of fibrosis markers. In addition, the NF-κB pathway could be induced, and inhibition of the NF-κB pathway could alleviate the fibrosis caused by MSNs. We conclude that inflammation is a major effector of the acute kidney toxicity induced by MSNs and results in renal interstitial fibrosis, which is mediated by the NF-κB signaling pathway.Keywords: mesoporous silica nanoparticles (MSNs), acute kidney injury, renal interstitial fibrosis, NF-κ

Why does oriental arborvitae grow better when mixed with black locust: Insight on nutrient cycling?

To identify why tree growth differs by afforestation type is a matter of prime concern in forestry. A study was conducted to determine why oriental arborvitae (Platycladus orientalis) grows better in the presence of black locust (Robinia pseudoacacia) than in monoculture. Different types of stands (i.e., monocultures and mixture of black locust and oriental arborvitae, and native grassland as a control) were selected in the Loess Plateau, China. The height and diameter at breast height of each tree species were measured, and soil, shoot, and root samples were sampled. The arbuscular mycorrhizal (AM) attributes, shoot and root nutrient status, height and diameter of black locust were not influenced by the presence of oriental arborvitae. For oriental arborvitae, however, growing in mixture increased height and diameter and reduced shoot Mn, Ca, and Mg contents, AM fungal spore density, and colonization rate. Major changes in soil properties also occurred, primarily in soil water, NO3-N, and available K levels and in soil enzyme activity. The increase in soil water, N, and K availability in the presence of black locust stimulated oriental arborvitae growth, and black locust in the mixed stand seems to suppress the development of AM symbiosis in oriental arborvitae roots, especially the production of AM fungal spores and vesicles, through improving soil water and N levels, thus freeing up carbon to fuel plant growth. Overall, the presence of black locust favored oriental arborvitae growth directly by improving soil water and fertility and indirectly by repressing AM symbiosis in oriental arborvitae roots

Strain-Promoted Catalyst-Free Click Chemistry for Rapid Construction of ⁶⁴Cu-Labeled PET Imaging Probes

A rapid, efficient, and catalyst-free click chemistry method for the construction of ⁶⁴Cu-labeled PET imaging probes was reported based on the strain-promoted aza-dibenzocyclooctyne ligation. This new method was exemplified in the synthesis of ⁶⁴Cu-labeled RGD peptide for PET imaging of tumor integrin α_vβ₃ expression <i>in vivo</i>. The catalyst-free click chemistry reaction proceeded with a fast rate and eliminated the contamination problem of the catalyst Cu­(I) ions interfering with the ⁶⁴Cu radiolabeling procedure under the conventional Cu-catalyzed 1,3-dipolar cycloaddition condition. The new strategy is simple and robust, and the resultant ⁶⁴Cu-labeled RGD probe was obtained in an excellent yield and high specific activity. PET imaging and biodistribution studies revealed significant, specific uptake of the “click” ⁶⁴Cu-labeled RGD probe in integrin α_vβ₃-positive U87MG xenografts with little uptake in nontarget tissues. This new approach is versatile, which warrants a wide range of applications for highly diverse radiometalated bioconjugates for radioimaging and radiotherapy