http://www.seavon.cn/rss/top Journal Aggregation RSS ,nature ,Science zh-cn2012-2-6 23:34:35SXNA(www.sxna.cn)(www.dc9.cn)Copyright 2005 sxna.cn, All rights reserved.Kenneth K.C. LeeTue,31 Jan 2012 06:30:00 +0800http://dx.doi.org/10.1002%2Fadma.201104170Ultrafast laser micromachining was optimized for microstructuringpolypyrrole as a facile new approach towards tailoring electrochemical and mechanical responses desirable for microactuator, sensors, neural probing, and nerve conduit applications. Laser perforation of high-density and high aspect ratio through-holes generated greater than 5-fold increase in surface area. The flexible machining technique offers micron-size resolution and fast prototyping capability for optimizing properties and opening new directions for polypyrrole-based devices.Assaf GalTue,31 Jan 2012 06:30:00 +0800http://dx.doi.org/10.1002%2Fadma.201104548Cystoliths are amorphous calcium carbonate bodies that form in the leaves of some plant families. Cystoliths are regularly distributed in the epidermis and protrude into the photosynthetic tissue, the mesophyll. The photosynthetic pigments generate a steep light gradient in the leaf. Under most illumination regimes the outer mesophyll is light saturated, thus the photosynthetic apparatus is kinetically unable to use the excess light for photochemistry. Here we use micro-scale modulated fluorometry to demonstrate that light scattered by the cystoliths is distributed from the photosynthetically inefficient upper tissue to the efficient, but light deprived, lower tissue. The results prove that the presence of light scatterers reduces the steep light gradient, thus enabling the leaf to use the incoming light flux more efficiently. MicroCT and electron microscopy confirm that the spatial distribution of the minerals is compatible with their optical function. During the study we encountered large calcium oxalate druses in the same anatomical location as the cystoliths. These druses proved to have similar light scattering functions as the cystoliths. This study shows that certain minerals in the leaves of different plants distribute the light flux more evenly inside the leaf.Leaf minerals function as internal light scatterersinside leaves. They transfer light from the saturated upper tissue into the light deprived lower tissue. This eases the steep light gradient inside the leaf and improves photosynthetic efficiency on the tissue scale.Qingchen DongTue,31 Jan 2012 03:10:00 +0800http://dx.doi.org/10.1002%2Fadma.201104171A polyferroplatinyne polymer can be patterned on the surface of Si wafer in ordered nanoline or nanodot shapes with PDMS molds through nanoimprint lithography (NIL), and subsequent thermal treatment gives rise to the nanopatterned arrays of L10-FePt nanoparticles with the same periodicities. The method offers excellent potential to be utilized in the simple and rapid fabrication of bit patterned media for magnetic data recording.Carl PfeifferTue,31 Jan 2012 03:10:00 +0800http://dx.doi.org/10.1002%2Fadma.201104290A direct transfer patterningprocess is presented that allows metallic patterns to be stamped onto a contoured substrate. This process was used to make some of the most efficient electrically small antennas to date, while maintaining bandwidths approaching the physical limit.Igor AharonovichTue,31 Jan 2012 02:51:00 +0800http://dx.doi.org/10.1002%2Fadma.201103932Homoepitaxial growth of single crystal diamond membranes is demonstrated employing a microwave plasma chemical vapor deposition technique. The membranes possess excellent structural, optical, and spin properties, which make them suitable for fabrication of optical microcavities for applications in quantum information processing, photonics, spintronics, and sensing.Peter CuonyMon,30 Jan 2012 06:40:00 +0800http://dx.doi.org/10.1002%2Fadma.201104578Nanometer wide silicon filaments embedded in an amorphous silicon oxide matrix are grown at low temperatures over a large area. The optical and electrical properties of these mixed-phase nanomaterials can be tuned independently, allowing for advanced light management in high efficiency thin-film silicon solar cells and for band-gap tuning via quantum confinement in third-generation photovoltaics.Balazs NemethMon,30 Jan 2012 06:40:00 +0800http://dx.doi.org/10.1002%2Fadma.201104345Real-time ion flux imaging: an ion-sensitive field-effect transistor (ISFET) array is coupled with optical microscopy to image the growth of, and ion flux through, micrometer-scale tubes and membranes built from polyoxometalate clusters. The correlation between the optical and ionic imaging data is excellent, showcasing the use of ISFET arrays for high-resolution spatial and temporal mapping of ionic movements.Torben DaenekeMon,30 Jan 2012 03:11:00 +0800http://dx.doi.org/10.1002%2Fadma.201104837Solar energy conversion efficiencies of over 4% have been achieved in DSCs constructed with aqueous electrolytes based on the ferricyanide–ferrocyanide redox couple, thereby avoiding the use of expensive, flammable and toxic solvents. This paradigm shift was made possible by the use of a hydrophobic organic carbazole dye.Maik R. J. SchererMon,30 Jan 2012 03:10:00 +0800http://dx.doi.org/10.1002%2Fadma.201104272Manufacturing V2O5 in a 3D periodic highly interconnected gyroidstructure on the 10 nm length scale is shown to lead to a significant electrochromic performance enhancement. The structured devices surpass previous inorganic electrochromic materials in all relevant parameters: the switching speed, coloration contrast, and composite coloration efficiency. In particular, the 85 ms switching speed lies within a factor of two of video rate. Enhanced ion intercalation into the gyroid morphology can be extended to other transition-metal oxides and is therefore promising for lithium ion batteries, supercapacitors, and sensors.Koji ChiyodaFri,27 Jan 2012 11:11:00 +0800http://dx.doi.org/10.1002%2Fanie.201109221Six in one blow: Total syntheses of all the amathaspiramide alkaloids have been accomplished. Rapid construction of the diazaspiro[3.3]nonane core combined with regio- and diastereoselective reduction of the cyclic imide moiety with DIBAL established the route to the common structural motif. The late-stage reduction of the lactam to an imine functionality mediated by Schwartz’s reagent was the key to the streamlined syntheses.Lantao LiuFri,27 Jan 2012 10:52:00 +0800http://dx.doi.org/10.1002%2Fanie.201108446In the nick of time: A nickel-catalyzed asymmetric intramolecular alkene insertion reaction into cyclobutanones (1) has been developed. The reaction significantly reduces the number of steps required for the synthesis of chiral benzobicyclo[2.2.2]octenones (2).Florie LavigneFri,27 Jan 2012 10:52:00 +0800http://dx.doi.org/10.1002%2Fanie.201108452Dismembering molecules: The stable boryl(phosphino)carbene 1 can cleave small organic dioxide molecules. With CO2 and SO2, 1 gives, respectively, the phosphacumulene ylide [Mes(iPr2N)B-O-P(CCO)(NiPr2)Mes] (see scheme and structure) and boryl(phosphoryl)sulfine [Mes(iPr2N)B-C(SO)-P(O)(NiPr2)Mes] which have been structurally and spectroscopically characterized.Reed T. LarsonFri,27 Jan 2012 10:52:00 +0800http://dx.doi.org/10.1002%2Fanie.201108227A tale of two Michaels: The first enantioselective total synthesis of (−)-GB17 is reported. Construction of this unique naphthoquinolizinone skeleton was achieved by two stereoselective intramolecular Michael additions, one under catalyst control and the other under substrate control.Swantje BehnkenFri,27 Jan 2012 10:52:00 +0800http://dx.doi.org/10.1002%2Fanie.201108214Anti-Terminator: Rise of the Molecules: Overexpression of an antiterminator gene (nusG) in Clostridium cellulolyticum induced the biosynthesis of the novel antibiotic closthioamide and related thioamides. This is the first successful genetic engineering of an anaerobe to trigger a cryptic pathway. Furthermore, synthetic probes provide valuable insights into the biogenetic relationship of the rare thioamide metabolites.Gary M. NoonanFri,27 Jan 2012 10:52:00 +0800http://dx.doi.org/10.1002%2Fanie.201108203Surprising selectivity: The first enantioselective hydroformylations of simple alkenes of type RCH2CHCH2 to preferentially deliver the branched aldehyde product have been discovered using a new chiral ligand, named bobphos (see scheme). Established ligands are unselective in this reaction or show a slight preference towards the linear aldehyde.Tuoqi WuFri,27 Jan 2012 10:52:00 +0800http://dx.doi.org/10.1002%2Fanie.201108336In the right light: UV light triggers bond breaking, liberates a caged carboxylic acid, and generates the central CC double bond in the photoresponsive hexatriene molecule of a dithienylethene molecular switch. Light of the same wavelength converts the colorless isomer to its colored counterpart (see picture) in a visually convenient method to report on the success of the release event.Graham R. DickFri,27 Jan 2012 10:52:00 +0800http://dx.doi.org/10.1002%2Fanie.201108608Problem solved: An air-stable 2-pyridyl borane that can effectively couple to a wide range of aryl and heteroaryl halides and pseudohalides has evaded the synthesis community for decades. The discovery that Cu(DEA)2 powerfully enables palladium-mediated cross-couplings with air-stable boronates 1 has finally provided a general solution to this very important problem. DEA=diethanolamine, DMF=N,N-dimethylformamide, Tf=trifluoromethanesulfonyl.Jianlong XiaFri,27 Jan 2012 10:51:00 +0800http://dx.doi.org/10.1002%2Fanie.201108167Strained: [6]Cycloparaphenylene, a molecule with 97 kcal mol−1 of strain energy, was synthesized. The synthetic strategy relied on two sequential oxidative dearomatization/addition sequences and a final reductive aromatization reaction (see scheme). The optoelectronic properties of [6]cycloparaphenylene were measured, and the analysis of the X-ray crystal structure revealed a linear packing geometry reminiscent of a carbon nanotube.Madleen SallmannFri,27 Jan 2012 10:51:00 +0800http://dx.doi.org/10.1002%2Fanie.201107345The natural paragon taken seriously: A trispyrazolylborato cysteinato iron complex not only excellently mimics the active site structure of cysteine dioxygenase (see picture: both structures superimposed): a dioxygenation of cysteinate occurs on treatment with O2, and hence, the system represents the hitherto most realistic model for cysteine dioxygenase.Eiji NakataFri,27 Jan 2012 10:51:00 +0800http://dx.doi.org/10.1002%2Fanie.201108199Point the finger: Zinc-finger proteins are convenient and site-selective adaptors for targeting specific locations within DNA-origami structures. Orthogonal targeting of the specific locations in the structures was demonstrated by using two adaptors, and the application of Escherichia coli lysate that contained the adaptor-fused proteins successfully afforded the expected protein–DNA assembly.Jianmin WangFri,27 Jan 2012 10:51:00 +0800http://dx.doi.org/10.1002%2Fanie.201107317Double agent: The title reaction using the guanidine catalyst 1 can deliver both enantiomers of the product with excellent enantioselectivity by judicious choice of the double bond geometry of the the β,-unsaturated carbonyl compound. Computational studies reveal the possible origin of the inversed enantioselectivity, and the potential for enantiodivergent synthesis chiral amine-containing substrates is attractive.Chao ChenFri,27 Jan 2012 10:51:00 +0800http://dx.doi.org/10.1002%2Fanie.201108663Fluorinated functionality: The copper-catalyzed oxidative trifluoromethylthiolation of aryl boronic acids with TMSCF3 and elemental sulfur at room temperature is described for the first time. This reaction provides a concise and efficient method for the synthesis of aryl trifluoromethyl thioethers (ArSCF3) under mild conditions.Alexander PatzerFri,27 Jan 2012 10:51:00 +0800http://dx.doi.org/10.1002%2Fanie.201108937The fundamentals: The IR spectrum of the adamantane cation, C10H16+, has been derived by resonant IR photodissociation of weakly bound C10H16+Ln clusters (see picture). The analysis of the IR spectrum provides the first spectroscopic characterization of this fundamental cycloalkane carbocation in the gas phase and direct evidence for the Jahn–Teller distortion in the 2A1 ground electronic state.Trung CaoFri,27 Jan 2012 10:51:00 +0800http://dx.doi.org/10.1002%2Fanie.201107417Saucy selection: The first catalytic, enantioselective Saucy–Marbet Claisen rearrangement has been achieved. Palladium(II) (R)-binap or tBuphox catalysts L*Pd(SbF6)2 were employed to generate allenyl oxindoles or spirolactones bearing a quaternary center with up to 98 % ee.