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时间: 2017年08月07日 | 作者: admin | 来源: 未知
1 Cash for carbon: A randomized trial of payments for ecosystem services to reduce deforestation 【地球科学】碳补偿:通过生态系统服务补偿减少森林 砍伐 的随机试验研究 Seema Jayachandran, Joost de Laat, Eric F

1 Cash for carbon: A randomized trial of payments for ecosystem services to reduce deforestation


Seema Jayachandran, Joost de Laat, Eric F. Lambin, Charlotte Y. Stanton, Robin Audy, Nancy E. Thomas



We evaluated a program of payments for ecosystem services in Uganda that offered forest-owning households annual payments of 70,000 Ugandan shillings per hectare if they conserved their forest. The program was implemented as a randomized controlled trial in 121 villages, 60 of which received the program for 2 years. The primary outcome was the change in land area covered by trees, measured by classifying high-resolution satellite imagery. We found that tree cover declined by 4.2% during the study period in treatment villages, compared to 9.1% in control villages. We found no evidence that enrollees shifted their deforestation to nearby land. We valued the delayed carbon dioxide emissions and found that this program benefit is 2.4 times as large as the program costs.


(导读 刘威尔)本研究评估了乌干达一个生态系统服务补偿项目,每年为不进行砍伐的林场主提供每公顷7万乌干达先令的补偿。结果显示,试验村庄森林覆盖面积减少4.2%而对照村庄减少9.1%,项目未导致砍伐活动转移至邻近森林,并带来2.4倍于补偿支出的减排收益。


2 Ratchet-like polypeptide translocation mechanism of the AAA+ disaggregase Hsp104


Stephanie N. Gates, Adam L. Yokom, JiaBei Lin…James Shorter, Daniel R. Southworth


Hsp100 polypeptide translocases are conserved members of the AAA+ family (adenosine triphosphatases associated with diverse cellular activities) that maintain proteostasis by unfolding aberrant and toxic proteins for refolding or proteolytic degradation. The Hsp104 disaggregase from Saccharomyces cerevisiae solubilizes stress-induced amorphous aggregates and amyloids. The structural basis for substrate recognition and translocation is unknown. Using a model substrate (casein), we report cryo–electron microscopy structures at near-atomic resolution of Hsp104 in different translocation states. Substrate interactions are mediated by conserved, pore-loop tyrosines that contact an 80-angstrom-long unfolded polypeptide along the axial channel. Two protomers undergo a ratchet-like conformational change that advances pore loop–substrate interactions by two amino acids. These changes are coupled to activation of specific nucleotide hydrolysis sites and, when transmitted around the hexamer, reveal a processive rotary translocation mechanism and substrate-responsive flexibility during Hsp104-catalyzed disaggregation.

(导读 刘思婕)酿酒酵母中含有的Hsp104解聚酶可以溶解由压力产生的非晶形聚合物和淀粉样蛋白。但此过程中底物识别和转位的结构基础仍然未知。本研究使用酪蛋白为模型底物得到了Hsp104在不同转位状态下的低温电子显微镜结构,揭示Hsp104催化解聚过程中的棘轮式转位机制。



3 Highly elastic binders integrating polyrotaxanes for silicon microparticle anodes in lithium ion batteries


Sunghun Choi, Tae-woo Kwon, Ali Coskun, Jang Wook Choi





Lithium-ion batteries with ever-increasing energy densities are needed for batteries for advanced devices and all-electric vehicles. Silicon has been highlighted as a promising anode material because of its superior specific capacity. During repeated charge-discharge cycles, silicon undergoes huge volume changes. This limits cycle life via particle pulverization and an unstable electrode-electrolyte interface, especially when the particle sizes are in the micrometer range. We show that the incorporation of 5 weight % polyrotaxane to conventional polyacrylic acid binder imparts extraordinary elasticity to the polymer network originating from the ring sliding motion of polyrotaxane. This binder combination keeps even pulverized silicon particles coalesced without disintegration, enabling stable cycle life for silicon microparticle anodes at commercial-level areal capacities.





4 Photoinduced decarboxylative borylation of carboxylic acids


Alexander Fawcett, Johan Pradeilles, Yahui Wang, Tatsuya Mutsuga, Eddie L. Myers, Varinder K. Aggarwal



The conversion of widely available carboxylic acids into versatile boronic esters would be highly enabling for synthesis. We found that this transformation can be effected by illuminating the N-hydroxyphthalimide ester derivative of the carboxylic acid under visible light at room temperature in the presence of the diboron reagent bis(catecholato)diboron. A simple workup allows isolation of the pinacol boronic ester. Experimental evidence suggests that boryl radical intermediates are involved in the process. The methodology is illustrated by the transformation of primary, secondary, and tertiary alkyl carboxylic acids as well as a diverse range of natural-product carboxylic acids, thereby demonstrating its broad utility and functional group tolerance.


(导读 卓思琪)羧酸转化为硼酸酯在合成中应用广泛。本文发现在双(邻苯二酚)二硼酸酯存在的情况下、室温条件可见光照射羧酸的N-羟基邻苯二甲酰亚胺酯衍生物可以实现该转换简单处理后能分离出频哪醇硼酸酯。实验证据显示该过程中涉及硼自由基中间体。研究对多种羧酸进行了实验证明该方法具有广泛适用性。


5 Bismuthene on a SiC substrate: A candidate for a high-temperature quantum spin Hall material


F. Reis, G. Li, L. Dudy…J. Schäfer, R. Claessen






Quantum spin Hall materials hold the promise of revolutionary devices with dissipationless spin currents but have required cryogenic temperatures owing to small energy gaps. Here we show theoretically that a room-temperature regime with a large energy gap may be achievable within a paradigm that exploits the atomic spin-orbit coupling. The concept is based on a substrate-supported monolayer of a high–atomic number element and is experimentally realized as a bismuth honeycomb lattice on top of the insulating silicon carbide substrate SiC(0001). Using scanning tunneling spectroscopy, we detect a gap of ~0.8 electron volt and conductive edge states consistent with theory. Our combined theoretical and experimental results demonstrate a concept for a quantum spin Hall wide-gap scenario, where the chemical potential resides in the global system gap, ensuring robust edge conductance.







6 Remobilization of crustal carbon may dominate volcanic arc emissions


Emily Mason, Marie Edmonds, Alexandra V. Turchyn






The flux of carbon into and out of Earth’s surface environment has implications for Earth’s climate and habitability. We compiled a global data set for carbon and helium isotopes from volcanic arcs and demonstrated that the carbon isotope composition of mean global volcanic gas is considerably heavier, at –3.8 to –4.6 per mil (‰), than the canonical mid-ocean ridge basalt value of –6.0‰. The largest volcanic emitters outgas carbon with higher δ13C and are located in mature continental arcs that have accreted carbonate platforms, indicating that reworking of crustal limestone is an important source of volcanic carbon. The fractional burial of organic carbon is lower than traditionally determined from a global carbon isotope mass balance and may have varied over geological time, modulated by supercontinent formation and breakup.






7 Chiral Majorana fermion modes in a quantum anomalous Hall insulator–superconductor structure


Qing Lin He, Lei Pan, Alexander L. Stern…Jing Xia, Kang L. Wang





Majorana fermion is a hypothetical particle that is its own antiparticle. We report transport measurements that suggest the existence of one-dimensional chiral Majorana fermion modes in the hybrid system of a quantum anomalous Hall insulator thin film coupled with a superconductor. As the external magnetic field is swept, half-integer quantized conductance plateaus are observed at the locations of magnetization reversals, giving a distinct signature of the Majorana fermion modes. This transport signature is reproducible over many magnetic field sweeps and appears at different temperatures. This finding may open up an avenue to control Majorana fermions for implementing robust topological quantum computing.





8 Experimentally realized mechanochemistry distinct from force-accelerated scission of loaded bonds


Sergey Akbulatov, Yancong Tian, Zhen Huang, Timothy J. Kucharski, Qing-Zheng Yang, Roman Boulatov



Stretching polymer chains accelerates dissociation of a variety of internal covalent bonds, to an extent that correlates well with the force experienced by the scissile bond. Recent theory has also predicted scenarios in which applied force accelerates dissociation of unloaded bonds and kinetically strengthens strained bonds. We report here unambiguous experimental validation of this hypothesis: Detailed kinetic measurements demonstrate that stretching phosphotriesters accelerates dissociation of the unloaded phosphorus-oxygen bond orthogonal to the pulling axis, whereas stretching organosiloxanes inhibits dissociation of the aligned loaded silicon-oxygen bonds. Qualitatively, the outcome is determined by phosphoester elongation and siloxane contraction along the pulling axis in the respective rate-determining transition states. Quantitatively, the results agree with a simple mechanochemical kinetics model.


(导读 卓思琪)理论假说认为,拉伸多聚物链可以加速多聚物内部未负载键的断裂,也可以稳定有负载键。本文证明了该假说:动力学测量表示,拉伸磷酸三酯加速了未负载磷-氧键断裂,而拉伸硅氧烷却抑制了有负载-氧键断裂。此结果可以用基本力学规律和模型进行定性定量解释。


9 Tailored semiconductors for high-harmonic optoelectronics


Murat Sivis Marco Taucer, Giulio Vampa…Claus Ropers, P. B. Corkum



The advent of high-harmonic generation in gases 30 years ago set the foundation for attosecond science and facilitated ultrafast spectroscopy in atoms, molecules, and solids. We explore high-harmonic generation in the solid state by means of nanostructured and ion-implanted semiconductors. We use wavelength-selective microscopic imaging to map enhanced harmonic emission and show that the generation medium and the driving field can be locally tailored in solids by modifying the chemical composition and morphology. This enables the control of high-harmonic technology within precisely engineered solid targets. We demonstrate customized high-harmonic wave fields with wavelengths down to 225 nanometers (ninth-harmonic order of 2-micrometer laser pulses) and present an integrated Fresnel zone plate target in silicon, which leads to diffraction-limited self-focusing of the generated harmonics down to 1-micrometer spot sizes.


(导读 刘思婕)本研究使用离子注入式的半导体纳米结构探究固体状态下的高次谐波生成。通过具有波长选择性的显微成像技术来检测加强型谐波发射,研究人员发现可以根据调整固体的化学组成和形态来定制生成介质和驱动场。研究结果使得在特定的固体目标上精准地控制高次谐波光电子成为可能




10 An organic-inorganic perovskite ferroelectric with large piezoelectric response


Yu-Meng You, Wei-Qiang Liao, Dewei Zhao…Yanfa Yan, Ren-Gen Xiong



Molecular piezoelectrics are highly desirable for their easy and environment-friendly processing, light weight, low processing temperature, and mechanical flexibility. However, although 136 years have passed since the discovery in 1880 of the piezoelectric effect, molecular piezoelectrics with a piezoelectric coefficient d33 comparable with piezoceramics such as barium titanate (BTO; ~190 picocoulombs per newton) have not been found. We show that trimethylchloromethyl ammonium trichloromanganese(II), an organic-inorganic perovskite ferroelectric crystal processed from aqueous solution, has a large d33 of 185 picocoulombs per newton and a high phase-transition temperature of 406 kelvin (K) (16 K above that of BTO). This makes it a competitive candidate for medical, micromechanical, and biomechanical applications.


(导读 刘思婕) 分子压电材料具有质量轻、加工温度低、机械性能灵活及对环境无害性质。目前人们尚未发现在压电系数上可以比拟压电陶瓷的分子压电材料。本研究发现氯甲基三甲铵三氯化锰(II),一种有机-无机钙钛矿铁电性晶体,兼具高压电系数和高相变温度的特点。 这种材料在医疗、微机械和生物机械等领域将具有广阔的应用前景。




11 Hydraulic control of tuna fins: A role for the lymphatic system in vertebrate locomotion


Vadim Pavlov, Benyamin Rosental, Nathaniel F. Hansen, Jody M. Beers, George Parish, Ian Rowbotham, Barbara A. Block



The lymphatic system in teleost fish has genetic and developmental origins similar to those of the mammalian lymphatic system, which is involved in immune response and fluid homeostasis. Here, we show that the lymphatic system of tunas functions in swimming hydrodynamics. Specifically, a musculo-vascular complex, consisting of fin muscles, bones, and lymphatic vessels, is involved in the hydraulic control of median fins. This specialization of the lymphatic system is associated with fish in the family Scombridae and may have evolved in response to the demand for swimming and maneuvering control in these high-performance species.


(导读 陈月欣) 硬骨鱼的淋巴系统与哺乳动物有着类似的起源,也起到了免疫应答与维持内稳态的作用。然而,本研究揭示了淋巴系统在鯖科鱼类中的独特功能:奇鳍中的肌肉、骨和淋巴管共同构成了一种可以控制水力的复合体,使得这类鱼可以在水中高效游动。


12 Bidirectional eukaryotic DNA replication is established by quasi-symmetrical helicase loading


Gideon Coster, John F. X. Diffley



Bidirectional replication from eukaryotic DNA replication origins requires the loading of two ring-shaped minichromosome maintenance (MCM) helicases around DNA in opposite orientations. MCM loading is orchestrated by binding of the origin recognition complex (ORC) to DNA, but how ORC coordinates symmetrical MCM loading is unclear. We used natural budding yeast DNA replication origins and synthetic DNA sequences to show that efficient MCM loading requires binding of two ORC molecules to two ORC binding sites. The relative orientation of these sites, but not the distance between them, was found to be critical for MCM loading in vitro and origin function in vivo. We propose that quasi-symmetrical loading of individual MCM hexamers by ORC and directed MCM translocation into double hexamers acts as a unifying mechanism for the establishment of bidirectional replication in archaea and eukaryotes.


(导读 郭怿暄)真核细胞中DNA的双向复制机制至今仍不清楚。本研究发现这一过程需要两个起点识别复合物(ORC)分别结合两个反向的ORC结合位点,继而进行微型染色体维持蛋白(MCM)解旋酶的准对称性装载,使得MCM转位形成稳定的二重六聚体。这一过程在古细菌和真核细胞中是保守的。




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