821 resultados para Commun


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对滇南和滇西茶叶害虫群落结构与生态分布进行了研究。该区域的茶叶害 虫隶属9 目, 57 科, 103 属, 167 种; 其中, 鳞翅目有16 科, 27 属, 53 种; 同翅目 13 科, 25 属, 35 种; 鞘翅目12 科, 23 属, 37 种; 直翅目4 科, 8 属, 17 种; 半翅 目4 科, 7 属, 10 种; 等翅目3 科, 5 属, 5 种; 缨翅目2 科, 4 属, 5 种; 竹节虫 目2 科, 2 属, 2 种; 双翅目1 科, 2 属, 3 种。同翅目、鳞翅目和鞘翅目的科、属、 种是整个茶园中优势类群; 直翅目、半翅目, 等翅目和缨翅目的科、属、种是茶叶 中常见类群; 竹节虫目和双翅目的科、属 种稀少。滇南和滇西的茶叶害虫绝大部 分属于东洋区成分种; 其生态类型可分为: 食嫩芽类型、食叶类型, 食果实类型, 为 害枝杆类型和食根及幼苗类型。

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Alternative promoter usage and alternative splicing enable diversification of the transcriptome. Here we demonstrate that the function of Synaptic GTPase-Activating Protein (SynGAP), a key synaptic protein, is determined by the combination of its amino-terminal sequence with its carboxy-terminal sequence. 5' rapid amplification of cDNA ends and primer extension show that different N-terminal protein sequences arise through alternative promoter usage that are regulated by synaptic activity and postnatal age. Heterogeneity in C-terminal protein sequence arises through alternative splicing. Overexpression of SynGAP α1 versus α2 C-termini-containing proteins in hippocampal neurons has opposing effects on synaptic strength, decreasing and increasing miniature excitatory synaptic currents amplitude/frequency, respectively. The magnitude of this C-terminal-dependent effect is modulated by the N-terminal peptide sequence. This is the first demonstration that activity-dependent alternative promoter usage can change the function of a synaptic protein at excitatory synapses. Furthermore, the direction and degree of synaptic modulation exerted by different protein isoforms from a single gene locus is dependent on the combination of differential promoter usage and alternative splicing.

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Nacre is a technologically remarkable organic-inorganic composite biomaterial. It consists of an ordered multilayer structure of crystalline calcium carbonate platelets separated by porous organic layers. This microstructure exhibits both optical iridescence and mechanical toughness, which transcend those of its constituent components. Replication of nacre is essential for understanding this complex biomineral, and paves the way for tough coatings fabricated from cheap abundant materials. Fabricating a calcitic nacre imitation with biologically similar optical and mechanical properties will likely require following all steps taken in biogenic nacre synthesis. Here we present a route to artificial nacre that mimics the natural layer-by-layer approach to fabricate a hierarchical crystalline multilayer material. Its structure-function relationship was confirmed by nacre-like mechanical properties and striking optical iridescence. Our biomimetic route uses the interplay of polymer-mediated mineral growth, combined with layer-by-layer deposition of porous organic films. This is the first successful attempt to replicate nacre, using CaCO(3).

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We present the characterisation of a hydrogel forming family of benzene 1,3,5-tricarboxamide (BTA) aromatic carboxylic acid derivatives. The simple, easy to synthesise compounds presented here exhibit consistent gel formation at low concentrations through the use of a pH trigger.

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Graphene is a single layer of covalently bonded carbon atoms, which was discovered only 8 years ago and yet has already attracted intense research and commercial interest. Initial research focused on its remarkable electronic properties, such as the observation of massless Dirac fermions and the half-integer quantum Hall effect. Now graphene is finding application in touch-screen displays, as channels in high-frequency transistors and in graphene-based integrated circuits. The potential for using the unique properties of graphene in terahertz-frequency electronics is particularly exciting; however, initial experiments probing the terahertz-frequency response of graphene are only just emerging. Here we show that the photoconductivity of graphene at terahertz frequencies is dramatically altered by the adsorption of atmospheric gases, such as nitrogen and oxygen. Furthermore, we observe the signature of terahertz stimulated emission from gas-adsorbed graphene. Our findings highlight the importance of environmental conditions on the design and fabrication of high-speed, graphene-based devices.

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Graphene is emerging as a viable alternative to conventional optoelectronic, plasmonic and nanophotonic materials. The interaction of light with charge carriers creates an out-of-equilibrium distribution, which relaxes on an ultrafast timescale to a hot Fermi-Dirac distribution, that subsequently cools emitting phonons. Although the slower relaxation mechanisms have been extensively investigated, the initial stages still pose a challenge. Experimentally, they defy the resolution of most pump-probe setups, due to the extremely fast sub-100 fs carrier dynamics. Theoretically, massless Dirac fermions represent a novel many-body problem, fundamentally different from Schrödinger fermions. Here we combine pump-probe spectroscopy with a microscopic theory to investigate electron-electron interactions during the early stages of relaxation. We identify the mechanisms controlling the ultrafast dynamics, in particular the role of collinear scattering. This gives rise to Auger processes, including charge multiplication, which is key in photovoltage generation and photodetectors.

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Alkali vapours, such as rubidium, are being used extensively in several important fields of research such as slow and stored light nonlinear optics quantum computation, atomic clocks and magnetometers. Recently, there is a growing effort towards miniaturizing traditional centimetre-size vapour cells. Owing to the significant reduction in device dimensions, light-matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for nonlinear interactions. Here, taking advantage of the mature platform of silicon photonics, we construct an efficient and flexible platform for tailored light-vapour interactions on a chip. Specifically, we demonstrate light-matter interactions in an atomic cladding waveguide, consisting of a silicon nitride nano-waveguide core with a rubidium vapour cladding. We observe the efficient interaction of the electromagnetic guided mode with the rubidium cladding and show that due to the high confinement of the optical mode, the rubidium absorption saturates at powers in the nanowatt regime.