462 research outputs found

    The Stable Picard Group of A(n)

    Full text link
    In this paper, we showed that the Stable Picard group of A(n)A(n) for n2n\geq 2 is ZZ\mathbb{Z}\oplus \mathbb{Z} by considering the endotrivial modules over A(n)A(n). The proof relies on reductions from a Hopf algebra to its proper Hopf subalgebras.Comment: 20 page

    Copper atomic contacts exposed to water molecules

    Get PDF
    Monatomic and molecular hydrogen and also oxygen, as well as water molecules and OH that are exposed to atomic copper in intimate contact have been studied theoretically using computational methods. The authors optimized moderately large structures of Cu/H/Cu, Cu/HCuH/Cu, Cu/H2_2/Cu, Cu/H2_2O/Cu, Cu/OH/Cu, Cu/O/Cu, Cu/O2_2/Cu, and calculated appropriate values for conductance and inelastic tunneling spectroscopy (IETS) properties of the contact junctions; elucidating them as being a possible outcome resulting from the exposure of copper electrodes to the atomic/molecular contaminant species. Here we also demonstrate the IETS properties, by means of ab-initio calculations, that can determine the form of the junction geometries. Furthermore, we identify the bonding geometries at the interfaces of the copper electrodes that directly give rise to the specific IETS signatures that have been observed in recent experiments. Based on low-bias conductance and IETS calculations, for the specific case of water exposure of copper electrodes, it was concluded that a single hydrogen or a single oxygen atom bridging the copper electrodes is not responsible for the high conductance peak measurements. Regarding Model 4, where an individual water molecule is considered to be the bridging constituent, our computational results suggest that it has a relatively low probability of being an appropriate candidate. Based upon current computational results, the two hydrogens in Model 3 appear to be in molecular form, although they still form a bond with the adjacent copper atoms. Comparing computational with experimental results indicates that Model 3 is in acceptable agreement with available data.Comment: 5 pages, 2 figure

    Hygienic Property and Water Resistance of Waterborne Polyacrylate/Flower-like ZnO Composite Coatings

    Get PDF
    Content: Polyacrylate as film-forming materials has been widely used in leather finishing, but its compactness significantly obstructs the hygienic property of upper leather. Therefore, considerable efforts have been made to endow polyacrylate with required properties. In this study, we demonstrated a facile and rapid sonochemical process to synthesis the flower-like ZnO nanostructures. The related morphology and structure of product were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Meanwhile, flower-like ZnO were introduced into the polyacrylate matrix by physical blending method, whose morphology, latex stability, water vapor permeability and water resistance were measured. The results showed that flower-like ZnO assembled by ellipsoid-like nanorods with the length of about 600 nm was successfully fabricated. The sizes of flower-like ZnO were 1.2 μm. According to SEM images, flower-like ZnO evenly dispersed were observed in composite matrix. Compared with pure polyacrylate, polyacrylate/flower-like ZnO composites exhibited the superior stability. Meanwhile, its water vapor permeability and water resistancewere increased by 52.91% and 53.13%, severally. The reason for this is that ZnO with rough structure can increase voids in polyacrylate film and thus improving hygienic property of polyacrylate film. Additionally, the hydrophilic groups on surface of ZnO can product the crosslinking with polyacrylate chains, which contributed to the enhancement of water resistance. Thus, a promising coating with hygienic property and water resistance for leather finishing agent was approved. Take-Away: 1. Polyacrylate/flower-like ZnO composites exhibited excellent hygienic property. 2. This composite coating achieves simultaneous enhancement in water vapor permeability and water resistance. 3. The morphology of ZnO can effect the properties of polyacrylate

    Specific DNA-RNA Hybrid Recognition by TAL Effectors

    Get PDF
    SummaryThe transcription activator-like (TAL) effector targets specific host promoter through its central DNA-binding domain, which comprises multiple tandem repeats (TALE repeats). Recent structural analyses revealed that the TALE repeats form a superhelical structure that tracks along the forward strand of the DNA duplex. Here, we demonstrate that TALE repeats specifically recognize a DNA-RNA hybrid where the DNA strand determines the binding specificity. The crystal structure of a designed TALE in complex with the DNA-RNA hybrid was determined at a resolution of 2.5 Å. Although TALE repeats are in direct contact with only the DNA strand, the phosphodiester backbone of the RNA strand is inaccessible by macromolecules such as RNases. Consistent with this observation, sequence-specific recognition of an HIV-derived DNA-RNA hybrid by an engineered TALE efficiently blocked RNase H-mediated degradation of the RNA strand. Our study broadens the utility of TALE repeats and suggests potential applications in processes involving DNA replication and retroviral infections

    Optimal coordinated operation of a multi-energy community considering interactions between energy storage and conversion devices

    Get PDF
    An optimal coordinated operation model of comprehensive energy storage and conversion devices was built by considering interdependency in a multi-vector energy community, to achieve an overall optimum. The model determined the storage size, the operation strategies of energy storage and conversion devices and scenario analysis was further conducted. The proposed sequential method solved the complex mixed-integer nonlinear programming (MINLP) problem by decomposing the multi-energy system into a subsystem of conversion devices and a PV-battery subsystem, which reduced the computation complexity. Firstly, electricity, heat and gas networks were modelled in an integrated manner and with a suitable level of detail for operational purposes. The integrated electrical-hydraulic-thermal-gas flow equations imposed by multi-energy networks were formulated as equality constraints in the optimization. The optimal operation of conversion technologies with increasing net-load variability on the consumer load profiles was determined. Secondly, the design and operation of PV-battery systems was investigated to provide economic incentives for storage owners. The total costs, the self-consumption ratio (SCR), the internal return rate (IRR) of PV-battery systems were calculated. In scenario analysis, interactions between multi-energy network operation limits as well as the impact of energy conversion devices on PV-battery systems were demonstrated. It showed that the option of Combined Heat and Power (CHP) was advantageous without considering PV-battery systems using 2016 financial data. However, considering the profit of PV-battery systems and the declining grid electricity carbon intensity, the option of heat pumps was advantageous and may be a favorable option in the long term

    A new experience mining approach for improving low carbon city development

    Full text link
    Developing low carbon city (LCC) has been widely appreciated as an important strategy for sustainable development. In line with this, an increasing number of cities globally have launched low carbon practices in recent years and gained various types of experience. However, it appears that existing studies do not present methods of how to use these valuable LCC experience in solving new problems. This study therefore introduces an experience mining approach to assist decision‐makers in reusing previous experience when tailoring LCC development strategies. The mining approach consists of three processes, namely, collecting historical cases which have been experiencing LCC, establishing LCC experience base, and mining similar experience cases. This study innovates the existing experience mining approach by introducing a two‐step mining process with considering the perspective of problem‐based urban characteristics (PBUCs) and the perspective of solution‐based urban characteristics (SBUCs). The application of the introduced mining approach has been demonstrated by a case study, where Shenyang’s energy structure is adopted as the target problem. The new experience mining approach provides a valuable reference for decision‐makers to retrieve similar cases for improving LCC development with the consideration of city characteristics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156189/2/sd2046_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156189/1/sd2046.pd

    Scaled-up biodiesel synthesis from Chinese Tallow Kernel oil catalyzed by Burkholderia cepacia lipase through ultrasonic assisted technology: A non-edible and alternative source of bio energy.

    Get PDF
    Abstract In East Asia, for thousands of years, the fruit of Chinese tallow tree ( Sapium sebiferum ) has been used for multiple purposes because of its chemical composition; the presence of high amounts of lipids is remarkable, showing potential to be used as substrate for biodiesel synthesis. Previously have been reported the use of alkaline and enzymatic catalysts, microwave technology and the use of ionic liquids as co-solvents with the lipids of this tree species to produce biodiesel. This study shows the results of the use of Burkholderia cepacia lipase as enzymatic catalyst for transesterification of Chinese Tallow Kernel oil (CTK), extracted from the fruit of Chinese tallow tree, into biodiesel, with the use of ultrasonic assisted technology and without the usage of solvents. The optimal operational parameters were determined and the reactions were developed in a batch reactor with the use of ultrasonic irradiation and emulsification to enhance the mass transfer. The scaled-up experiments, in an especially designed 3 L capacity reactor, showed promising results, obtaining 55.20% biodiesel and a kinematic viscosity of 10.31 mm 2 .s −1 in only 4 h, in comparison with previously published ( in vitro ) methods. The valorization of this non-edible source of oil represents an opportunity to use as an alternative source for bioenergy and also to tackle the uncontrolled expansion of this oleaginous tree species in some ecologically fragile ecosystems

    Chlorine corrosion of blast furnace gas pipelines: analysis from thermal perspective

    Get PDF
    With the broad application of dry dedusting of blast furnace gas(BFG), the issue of BFG pipeline corrosion comes up because of chlorine in the BFG. Existing methods in preventing the corrosion, such as spraying alkali or installing corrosion-resistant materials, require a significant amount of investment. This paper conducted a novel thermal analysis of the corrosion mechanism to support the study on corrosion prevention without using additional materials. Firstly, thermal models were established to reflect the relationships among the amount of condensation water, the mass transfer rate, the concentration of chloride ion and the ambient temperature. Secondly, the relationship between BFG temperature and the corrosion rate was obtained via a cyclic exposure experiment. Key factors that affect the pipeline corrosion under various BFG temperatures were identified. Finally, a control scheme of the BFG temperature was proposed to avoid the chlorine corrosion
    corecore