Development of adenocarcinomas after transplantation of rat glandular stomachs treated in vitro with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)

Cellular and Molecular Life Sciences - Glandular stomachs of fetal and newborn Wistar rats were transplanted s.c. after treatment in vitro with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) at...     

Dysregulation of the TSC-mTOR pathway in human disease

The mammalian target of rapamycin (mTOR) has a central role in the regulation of cell growth. mTOR receives input from multiple signaling pathways, including growth factors and nutrients, to stimulate protein synthesis by phosphorylating key translation regulators such as ribosomal S6 kinase and eukaryote initiation factor 4E binding protein 1. High levels of dysregulated mTOR activity are associated with several hamartoma syndromes, including tuberous sclerosis complex, the PTEN-related hamartoma syndromes and Peutz-Jeghers syndrome. These disorders are all caused by mutations in tumor-suppressor genes that negatively regulate mTOR. Here we discuss the emerging evidence for a functional relationship between the mTOR signaling pathway and several genetic diseases, and we present evidence supporting a model in which dysregulation of mTOR may be a common molecular basis, not only for hamartoma syndromes, but also for other cellular hypertrophic disorders.     

Tunable gold catalysts for selective hydrocarbon oxidation under mild conditions

Oxidation is an important method for the synthesis of chemical intermediates in the manufacture of high-tonnage commodities, high-value fine chemicals, agrochemicals and pharmaceuticals: but oxidations are often inefficient. The introduction of catalytic systems using oxygen from air is preferred for 'green' processing. Gold catalysis is now showing potential in selective redox processes, particularly for alcohol oxidation and the direct synthesis of hydrogen peroxide. However, a major challenge that persists is the synthesis of an epoxide by the direct electrophilic addition of oxygen to an alkene. Although ethene is epoxidized efficiently using molecular oxygen with silver catalysts in a large-scale industrial process, this is unique because higher alkenes can only be effectively epoxidized using hydrogen peroxide, hydroperoxides or stoichiometric oxygen donors. Here we show that nanocrystalline gold catalysts can provide tunable active catalysts for the oxidation of alkenes using air, with exceptionally high selectivity to partial oxidation products ( approximately 98%) and significant conversions. Our finding significantly extends the discovery by Haruta that nanocrystalline gold can epoxidize alkenes when hydrogen is used to activate the molecular oxygen; in our case, no sacrificial reductant is needed. We anticipate that our finding will initiate attempts to understand more fully the mechanism of oxygen activation at gold surfaces, which might lead to commercial exploitation of the high redox activity of gold nanocrystals.     

The receptors and coding logic for bitter taste

The sense of taste provides animals with valuable information about the nature and quality of food. Bitter taste detection functions as an important sensory input to warn against the ingestion of toxic and noxious substances. T2Rs are a family of approximately 30 highly divergent G-protein-coupled receptors (GPCRs) that are selectively expressed in the tongue and palate epithelium and are implicated in bitter taste sensing. Here we demonstrate, using a combination of genetic, behavioural and physiological studies, that T2R receptors are necessary and sufficient for the detection and perception of bitter compounds, and show that differences in T2Rs between species (human and mouse) can determine the selectivity of bitter taste responses. In addition, we show that mice engineered to express a bitter taste receptor in 'sweet cells' become strongly attracted to its cognate bitter tastants, whereas expression of the same receptor (or even a novel GPCR) in T2R-expressing cells resulted in mice that are averse to the respective compounds. Together these results illustrate the fundamental principle of bitter taste coding at the periphery: dedicated cells act as broadly tuned bitter sensors that are wired to mediate behavioural aversion.     

引射式压力恢复系统的振动抑制技术

为了提高引射式压力恢复系统振动抑制性能,减小本系统振动对其他系统的影响,分析了系统的振动特性和振型,建立了系统振动力和主振型数学模型,利用时域信号取均方根方法测试了系统3个支座动态振动力,振动力沿气流方向逐渐减小。采用被动控制振动抑制技术,根据振动力设计制作了减振器,研究了橡胶块与金属弹簧并联再加配重以及橡胶块加配重2种减振器模型的减振效果。结果表明:橡胶块与金属弹簧并联、加配重45.2kg的减振器模型减振效果好,当控制点输入加速度为5 g时,减振效果最佳。激励强度大小、弹簧刚度和阻尼等参数的优化能够提高减振器的减振性能。     

Differential roles of MDA5 and RIG-I helicases in the recognition of RNA viruses

The innate immune system senses viral infection by recognizing a variety of viral components (including double-stranded (ds)RNA) and triggers antiviral responses. The cytoplasmic helicase proteins RIG-I (retinoic-acid-inducible protein I, also known as Ddx58) and MDA5 (melanoma-differentiation-associated gene 5, also known as Ifih1 or Helicard) have been implicated in viral dsRNA recognition. In vitro studies suggest that both RIG-I and MDA5 detect RNA viruses and polyinosine-polycytidylic acid (poly(I:C)), a synthetic dsRNA analogue. Although a critical role for RIG-I in the recognition of several RNA viruses has been clarified, the functional role of MDA5 and the relationship between these dsRNA detectors in vivo are yet to be determined. Here we use mice deficient in MDA5 (MDA5-/-) to show that MDA5 and RIG-I recognize different types of dsRNAs: MDA5 recognizes poly(I:C), and RIG-I detects in vitro transcribed dsRNAs. RNA viruses are also differentially recognized by RIG-I and MDA5. We find that RIG-I is essential for the production of interferons in response to RNA viruses including paramyxoviruses, influenza virus and Japanese encephalitis virus, whereas MDA5 is critical for picornavirus detection. Furthermore, RIG-I-/- and MDA5-/- mice are highly susceptible to infection with these respective RNA viruses compared to control mice. Together, our data show that RIG-I and MDA5 distinguish different RNA viruses and are critical for host antiviral responses.     

Analysis of the DNA sequence and duplication history of human chromosome 15

Here we present a finished sequence of human chromosome 15, together with a high-quality gene catalogue. As chromosome 15 is one of seven human chromosomes with a high rate of segmental duplication, we have carried out a detailed analysis of the duplication structure of the chromosome. Segmental duplications in chromosome 15 are largely clustered in two regions, on proximal and distal 15q; the proximal region is notable because recombination among the segmental duplications can result in deletions causing Prader-Willi and Angelman syndromes. Sequence analysis shows that the proximal and distal regions of 15q share extensive ancient similarity. Using a simple approach, we have been able to reconstruct many of the events by which the current duplication structure arose. We find that most of the intrachromosomal duplications seem to share a common ancestry. Finally, we demonstrate that some remaining gaps in the genome sequence are probably due to structural polymorphisms between haplotypes; this may explain a significant fraction of the gaps remaining in the human genome.     

汽轮发电机组振动故障诊断的模糊输入方法

针对汽轮发电机组振动故障的特点,构造了一模糊神经网络（ＦＮＮ）诊断模型,讨论了网络的多种模糊化输入,输出方式,并对两种模糊输入方法进行了对比分析。最后运用该诊断方法与传统的ＢＰ网络诊断方法进行比较。结果表明：模糊神经网络诊断方法对汽轮发电机组振动故障的识别是有效的,且在分类模糊边界数据时优于ＢＰ网络诊断方法。     

C-RAN架构下一种基于分形定理的载波迁移预测算法

作为C-RAN关键技术之一的实时虚拟化技术要求实现硬件处理资源的虚拟化管理,实现物理资源的动态分配和负载均衡,保证虚拟基站的实时性,处理时延和抖动可控。为提高物理资源的动态分配和负载均衡的效率,在传统虚拟机迁移策略基础上结合分形理论,提出一种动态载波迁移预测算法,避免了因瞬时负载峰值触发载波迁移而带来不必要的迁移开销。该算法通过对物理资源负载离散历史数据进行分形拼贴拟合出完整负载曲线,然后根据分形维度不变性实现对未来数据的预测。为实现对该算法的仿真,结合C-RAN的系统架构搭建了一个基于并行离散事件仿真(parallel discrete event simulation PDES)的验证平台,仿真结果表明该算法能在有效减少虚拟基站迁移次数的同时确保达到负载均衡的目的。     

时变OFDM稀疏信道估计中最优导频选择

针对时变OFDM系统中基于压缩感知的频率选择性衰落信道估计,为了提高其估计精度,结合最优导频选择方式,给出一种自适应求最优导频方法。通过闭环反馈信道稀疏度变化的方式,实时的求取最优导频进行信道估计,并与周期性求最优导频方法进行对比分析。仿真结果表明,自适应方法具有更低的信道估计均方误差,与随机方式相比,性能增益平均提高了11 dB,比周期性方法,平均提高了4 dB,且自适应方法误差曲线更平滑。