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Re-visiting the O/Cu(111) system – when metastable surface oxides could become an issue!
Richter, Norina A.,Kim, Chang-Eun,Stampfl, Catherine,Soon, Aloysius The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.48
<P>Surface oxidation processes are crucial for the functionality of Cu-based catalytic systems used for methanol synthesis, partial oxidation of methanol or the water-gas shift reaction. We assess the stability and population of the “8”-structure, a <IMG SRC='http://www.rsc.org/ej/CP/2014/c4cp04473h/c4cp04473h-t1.gif'> oxide phase, on the Cu(111) surface. This structure has been observed in X-ray photoelectron spectroscopy and low-energy electron diffraction experiments as a Cu(111) surface reconstruction that can be induced by a hyperthermal oxygen molecular beam. Using density-functional theory calculations in combination with <I>ab initio</I> atomistic thermodynamics and Boltzmann statistical mechanics, we find that the proposed oxide superstructure is indeed metastable and that the population of the “8”-structure is competitive with the known “29” and “44” oxide film structures on Cu(111). We show that the configuration of O and Cu atoms in the first and second layers of the “8”-structure closely resembles the arrangement of atoms in the first two layers of Cu<SUB>2</SUB>O(110), where the atoms in the “8”-structure are more constricted. Cu<SUB>2</SUB>O(110) has been suggested in the literature as the most active low index facet for reactions such as water splitting under light illumination. If the “8”-structure were to form during a catalytic process, it is therefore likely to be one of the reactive phases.</P> <P>Graphic Abstract</P><P>Using DFT calculations in combination with <I>ab initio</I> atomistic thermodynamics and Boltzmann statistical mechanics, a new metastable oxidized surface structure on Cu(111) has been identified and our theoretical results support observations made by experiments. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp04473h'> </P>
Microporous Ceramic Membranes - on the Way to Large Scale Application
H. Richter,U. Lubenau,P. Puhlfürß,Ch. Pflieger,M. Weyd,R. Mothes,D. Worch,I. Voigt,A. Michaelis 한국막학회 2017 한국막학회 총회 및 학술발표회 Vol.2017 No.11
High membrane costs hinders large scale application of microporous ceramic membranes. Preparation on elements of large specific membrane area are a prospective strategy to overcome this problem. NF membranes with a cut-off of 450 Da were produced for first time in a 163-channel tube geometry of 1.25 m². The membranes were successful tested in drink water production and in treatment of produced water from oil production. Zeolite-NaA-membranes were prepared for the first time inside of 1.2 m long tubes in four channel geometry of 0.9 m². Natural gas is dried by stripping with triethylene glycol (TEG). TEG will be regenerated by distillation at 190°C to 205°C. A pilot plant for TEG drying with Zeolite-NaAmembranes at 120°C for a capacity of 10.000 m³/h natural gas and is running since October 2016.
Udagawa, T.,Swanger, Sharon A.,Takeuchi, K.,Kim, J.,Nalavadi, V.,Shin, J.,Lorenz, Lori J.,Zukin, R.,Bassell, Gary J.,Richter, Joel D. Cell Press 2012 Molecular cell Vol.47 No.2
Translational control of mRNAs in dendrites is essential for certain forms of synaptic plasticity and learning and memory. CPEB is an RNA-binding protein that regulates local translation in dendrites. Here, we identify poly(A) polymerase Gld2, deadenylase PARN, and translation inhibitory factor neuroguidin (Ngd) as components of a dendritic CPEB-associated polyadenylation apparatus. Synaptic stimulation induces phosphorylation of CPEB, PARN expulsion from the ribonucleoprotein complex, and polyadenylation in dendrites. A screen for mRNAs whose polyadenylation is altered by Gld2 depletion identified >100 transcripts including one encoding NR2A, an NMDA receptor subunit. shRNA depletion studies demonstrate that Gld2 promotes and Ngd inhibits dendritic NR2A expression. Finally, shRNA-mediated depletion of Gld2 in vivo attenuates protein synthesis-dependent long-term potentiation (LTP) at hippocampal dentate gyrus synapses; conversely, Ngd depletion enhances LTP. These results identify a pivotal role for polyadenylation and the opposing effects of Gld2 and Ngd in hippocampal synaptic plasticity.
구상모,최창용,조원주,김상식,Qiliang Li,John S. Suehle,Curt A. Richter,Eric M. Vogel 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3
In this paper, we report an approach based on three-dimensional numerical simulations for the investigation of the dependence of the on/off current ratio in silicon nanowire (SiNW) field-effect transistors (FETs) on the channel width. In order to investigate the transport behavior in devices with different channel geometries, we have performed detailed two-dimensional and three-dimensional simulations of SiNWFETs and control FETs with a fixed channel length L and thickness t but varying the channel width W from 5 nm and 5 μm. By evaluating the charge distributions and the current flowlines of both the two- and three-dimensional structures, we have shown that the increase in the `on state' conduction current in the SiNW channel is a dominant factor, which consequently results in more than a two order of magnitude improvement in the on/off current ratio. In this paper, we report an approach based on three-dimensional numerical simulations for the investigation of the dependence of the on/off current ratio in silicon nanowire (SiNW) field-effect transistors (FETs) on the channel width. In order to investigate the transport behavior in devices with different channel geometries, we have performed detailed two-dimensional and three-dimensional simulations of SiNWFETs and control FETs with a fixed channel length L and thickness t but varying the channel width W from 5 nm and 5 μm. By evaluating the charge distributions and the current flowlines of both the two- and three-dimensional structures, we have shown that the increase in the `on state' conduction current in the SiNW channel is a dominant factor, which consequently results in more than a two order of magnitude improvement in the on/off current ratio.
Hyun, Y.,Richter, R.,Vincent, C.,Martinez-Gallegos, R.,Porri, A.,Coupland, G. ELSEVIER SCIENCE B.V. AMSTERDAM 2016 DEVELOPMENTAL CELL Vol.37 No.3
Flowering is initiated in response to environmental and internal cues that are integrated at the shoot apical meristem (SAM). We show that SPL15 coordinates the basal floral promotion pathways required for flowering of Arabidopsis in non-inductive environments. SPL15 directly activates transcription of the floral regulators FUL and miR172b in the SAM during floral induction, whereas its paralog SPL9 is expressed later on the flanks of the SAM. The capacity of SPL15 to promote flowering is regulated by age through miR156, which targets SPL15 mRNA, and gibberellin (GA), which releases SPL15 from DELLAs. Furthermore, SPL15 and the MADS-box protein SOC1 cooperate to promote transcription of their target genes. SPL15 recruits RNAPII and MED18, a Mediator complex component, in a GA-dependent manner, while SOC1 facilitates active chromatin formation with the histone demethylase REF6. Thus, we present a molecular basis for assimilation of flowering signals and transcriptional control at the SAM during flowering.
Noise in ZnO nanowire field effect transistors.
Xiong, Hao D,Wang, Wenyong,Suehle, John S,Richter, Curt A,Hong, Woong-Ki,Lee, Takhee American Scientific Publishers 2009 Journal of Nanoscience and Nanotechnology Vol.9 No.2
<P>The noise power spectra in ZnO nanowire field effect transistors (FETs) were experimentally investigated and showed a classical 1/f dependence. A Hooge's constant of 5 x 10(-3) was estimated. This value is within the range reported for CMOS FETs with high-k dielectrics, supporting the concept that nanowires can be utilized for future beyond-CMOS electronic applications from the point of view of device noise properties. ZnO FETs measured in a dry O2 environment displayed elevated noise levels compared to in vacuum. At low temperature, random telegraph signals are observed in the drain current.</P>
Fine structure of the isoscalar giant quadrupole resonance inSi28andAl27
Usman, I. T.,Buthelezi, Z.,Carter, J.,Cooper, G. R. J.,Fearick, R. W.,Fö,rtsch, S. V.,Fujita, H.,Fujita, Y.,von Neumann-Cosel, P.,Neveling, R.,Papakonstantinou, P.,Pysmenetska, I.,Richter, A.,Roth American Physical Society 2016 Physical Review C Vol.94 No.2
<P>The isoscalar giant quadrupole resonance in Si-28 and Al-27 has been investigated with high-energy-resolution proton inelastic scattering at E-p = 200 MeV and at scattering angles close to the maximum of Delta L = 2 angular distributions with the K600 magnetic spectrometer of iThemba LABS, South Africa. Characteristic scales are extracted from the observed fine structure with a wavelet analysis and compared for Si-28 with random-phase approximation and second random phase approximation calculations with an interaction derived from the Argonne V18 potential by a unitary transformation. A recent extension of the method to deformed nuclei provides the best description of the data, suggesting the significance of Landau damping.</P>
Lee, C.,Richter, A.,Lee, H.,Kim, Y.J.,Burrows, J.P.,Lee, Y.G.,Choi, B.C. Pergamon Press ; Elsevier [distribution] 2008 Atmospheric environment Vol.42 No.7
The East Asian countries have been affected by atmospheric gaseous pollutants (in particular SO<SUB>2</SUB>) transported from the Asian continent as well as Asian dust storms. For investigation of the impact of these anthropogenic trace gases on local air quality in Korea, ground-based measurements using a Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) system and in situ gas analyzers as well as synoptic meteorological data and scattered sunlight spectra obtained by the satellite-borne instrument, Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) launched on board of Environmental Satellite (ENVISAT) in March 2002, were utilized to retrieve SO<SUB>2</SUB> and trace its transport from the Asian continent to Korea in May 2005. The ground-based measurements were carried out in the region of interest, at Korea Global Watch Observatory (KGAWO) in Korea. Plumes of high SO<SUB>2</SUB> over Chinese industrial areas and their transport to the Korean peninsula were observed in SCIAMACHY data in the period of 21-26 May 2005. Highly increased SO<SUB>2</SUB> was measured by the MAX-DOAS system and in situ gas analyzer in the period of 27-29 May 2005 at KGAWO. These observations are supported by the meteorological results that the air-masses picking up these high SO<SUB>2</SUB> plumes while passing over the Chinese industrial and metropolitan areas were transported to the Korean peninsula. The tropospheric SO<SUB>2</SUB> VCDs over these Chinese industrial and metropolitan areas ranged up to 1.4x10<SUP>17</SUP>molcm<SUP>-2</SUP> in SCIAMACHY data. These SO<SUB>2</SUB> plumes resulted in increased SO<SUB>2</SUB> surface levels of up to 7.8ppbv (measured by an in situ gas analyzer) at KGAWO.