Dynamic admittance of atomic wires

We have investigated the low-frequency admittance of quantum wires in which a section consists of several Al atoms. The atomic section is connected to two three-dimensional leads that are modeled by the jellium model. The quantum scattering problem is solved by combining the first-principles ab initio method with a transfer-matrix evaluation of the scattering matrix. The ac admittance is then computed by evaluating various partial densities of states. The nature of the ac responses are predicted for these Al atomic wires.published_or_final_versio

Insight into biochar properties and its cost analysis

© 2015 Elsevier Ltd. Biochars (BCs) are widely produced and used for the remediation of environmental contaminants as bio-sorbents. In this review, statistical analysis of different BC physico-chemical properties was conducted. It was observed that woody materials are the most suitable for preparing BCs, among many other potential raw materials such as food wastes and agricultural materials. Currently BCs are produced through a variety of thermal treatment processes between 300 and 900 °C, among which slow pyrolysis is widely used due to its moderate operating conditions and optimization of BC yields. Hydrothermal carbonisation (HTC) is also an effective approach for BC production under certain conditions. As pyrolysis temperature is increased, the carbon content, ash content, surface area, and pore volume tend to be increased while the yield, hydrogen, oxygen, nitrogen content, and H/C and O/C molar ratios tend to decrease. The economic feasibility of BCs depends on a range of factors from raw material price to efficient production technologies. Thus, the overall cost equation of a pilot BC production plant together with the cost equation for BC regeneration has been proposed. The future research directions of BCs are also elaborated

Proposal for optical parity state re-encoder

We propose a re-encoder to generate a refreshed parity encoded state from an existing parity encoded state. This is the simplest case of the scheme by Gilchrist et al. (Phys. Rev. A 75, 052328). We show that it is possible to demonstrate with existing technology parity encoded quantum gates and teleportation.Comment: 8 pages, 4 figure

Adsorptive removal of antibiotics from water and wastewater: Progress and challenges

© 2015 Elsevier B.V. Antibiotics as emerging contaminants are of global concern due to the development of antibiotic resistant genes potentially causing superbugs. Current wastewater treatment technology cannot sufficiently remove antibiotics from sewage, hence new and low-cost technology is needed. Adsorptive materials have been extensively used for the conditioning, remediation and removal of inorganic and organic hazardous materials, although their application for removing antibiotics has been reported for ~30 out of 250 antibiotics so far. The literature on the adsorptive removal of antibiotics using different adsorptive materials is summarized and critically reviewed, by comparing different adsorbents with varying physicochemical characteristics. The efficiency for removing antibiotics from water and wastewater by different adsorbents has been evaluated by examining their adsorption coefficient (Kd) values. For sulfamethoxazole the different adsorbents followed the trend: biochar (BC)>multi-walled carbon nanotubes (MWCNTs)>graphite=clay minerals, and for tetracycline the adsorptive materials followed the trend: SWCNT>graphite>MWCNT=activated carbon (AC)>bentonite=humic substance=clay minerals. The underlying controlling parameters for the adsorption technology have been examined. In addition, the cost of preparing adsorbents has been estimated, which followed the order of BCs<ACs<ion exchange resins<MWCNTs<SWCNTs. The future research challenges on process integration, production and modification of low-cost adsorbents are elaborated

Quantum transport through atomic wires

We have investigated quantum transport through long wires in which a section consists of one or several Al atoms in a chain. The self-consistent ground state electronic potential is obtained using the first principles ab initio method and the conductance is calculated by solving a three-dimensional quantum scattering problem. We have observed quantized conductance when there are two or more Al atoms in the chain. Resistance is calculated for these wires at the Fermi level. ©1997 American Institute of Physics.published_or_final_versio

Structural and transport properties of aluminum atomic wires

We report a first-principles calculation of structural properties and quantum conductance of aluminum atomic wires. Our data together with a simple model allows us to predict the behavior of the elastic constant C11 as a function of the cross-sectional size of the free-standing wires. The quantum molecular dynamics, performed at both 0 and 300 K, provides information concerning the stability of these atomic wires. For the most stable wire, relaxation at 0 K causes a change of approximately 2-4 % in atomic positions, and room temperature contributes another 4–6 %. We obtain the quantum conductance of these wires by combining density functional theory and a three-dimensional evaluation of the scattering matrix. The structures obtained from the quantum molecular-dynamics simulations are examined and transport properties compared.published_or_final_versio

Efficient electrocatalytic oxygen reduction reaction of thermally optimized carbon black supported zeolitic imidazolate framework nanocrystals under low-temperature

Turning commercially available low-cost conducting carbon black materials into functional electrocatalytic electrode media using simple surface chemical modification is a highly attractive approach. This study reports on remarkably enhanced oxygen electrocatalytic activity of commercially available Ketjenblack (KB) by growing a non-precious cobalt metal-based zeolitic-imidazolate framework (ZIF-67) at room temperature in methanol solution followed by a mild thermolysis. The resulting Co@CoOx nanoparticle decorated nitrogen-doped KB derived from the optimized ZIF-67 : KB weight ratio of hybrid samples at 500-600 °C shows high performance for the oxygen reduction reaction (ORR) with impressive Eonset and E1/2 values of ∼0.90 and ∼0.83 V (vs. RHE), respectively in 0.1 M KOH electrolyte. Such ORR activity is comparable to, or better than many metal@metal-oxide-carbon based electrocatalysts synthesized under elevated carbothermal temperatures and using multicomponent/multistep chemical modification conditions. Therefore, a simple electrocatalyst design reported in this work is an efficient synthesis route that not only utilises earth-abundant carbon black but also comprises scalable room temperature synthesized ZIF-67 following mild thermolysis conditions under 600 °C

Decoherence Dynamics of Measurement-Induced Nonlocality and comparison with Geometric Discord for two qubit systems

We check the decoherence dynamics of Measurement-induced Nonlocality(in short, MIN) and compare it with geometric discord for two qubit systems. There are quantum states, on which the action of dephasing channel cannot destroy MIN in finite or infinite time. We check the additive dynamics of MIN on a qubit state under two independent noise. Geometric discord also follows such additive dynamics like quantum discord. We have further compared non-Markovian evolution of MIN and geometric discord under dephasing and amplitude damping noise for pure state and it shows distinct differences between their dynamics.Comment: 11 pages, 10 figures, Revte

Capacitance of Atomic Junctions

We report the behavior of the electrochemical capacitance for a variety of atomic junctions using ab initio methods. The capacitance can be classified according to the nature of conductance and shows a remarkable crossover from a quantum dominated regime to that of a classical-like geometric behavior. Clear anomalies arise due to a finite density of states of the atomic junction as well as the role played by the atomic valence orbitals. The results suggest several experiments to study contributions due to quantum effects and the atomic degree of freedom.published_or_final_versio

Progress in the biological and chemical treatment technologies for emerging contaminant removal from wastewater: A critical review

© 2016 Elsevier B.V. This review focuses on the removal of emerging contaminants (ECs) by biological, chemical and hybrid technologies in effluents from wastewater treatment plants (WWTPs). Results showed that endocrine disruption chemicals (EDCs) were better removed by membrane bioreactor (MBR), activated sludge and aeration processes among different biological processes. Surfactants, EDCs and personal care products (PCPs) can be well removed by activated sludge process. Pesticides and pharmaceuticals showed good removal efficiencies by biological activated carbon. Microalgae treatment processes can remove almost all types of ECs to some extent. Other biological processes were found less effective in ECs removal from wastewater. Chemical oxidation processes such as ozonation/H2O2, UV photolysis/H2O2 and photo-Fenton processes can successfully remove up to 100% of pesticides, beta blockers and pharmaceuticals, while EDCs can be better removed by ozonation and UV photocatalysis. Fenton process was found less effective in the removal of any types of ECs. A hybrid system based on ozonation followed by biological activated carbon was found highly efficient in the removal of pesticides, beta blockers and pharmaceuticals. A hybrid ozonation-ultrasound system can remove up to 100% of many pharmaceuticals. Future research directions to enhance the removal of ECs have been elaborated