Theory of Activated Transport in Bilayer Quantum Hall Systems

We analyze the transport properties of bilayer quantum Hall systems at total filling factor $\nu=1$ in drag geometries as a function of interlayer bias, in the limit where the disorder is sufficiently strong to unbind meron-antimeron pairs, the charged topological defects of the system. We compute the typical energy barrier for these objects to cross incompressible regions within the disordered system using a Hartree-Fock approach, and show how this leads to multiple activation energies when the system is biased. We then demonstrate using a bosonic Chern-Simons theory that in drag geometries, current in a single layer directly leads to forces on only two of the four types of merons, inducing dissipation only in the drive layer. Dissipation in the drag layer results from interactions among the merons, resulting in very different temperature dependences for the drag and drive layers, in qualitative agreement with experiment.Comment: 4 pages, 2 figure

Polarization transitions in interacting ring 1D arrays

Periodic nanostructures can display the dynamics of arrays of atoms while enabling the tuning of interactions in ways not normally possible in Nature. We examine one dimensional arrays of a ``synthetic atom,'' a one dimensional ring with a nearest neighbor Coulomb interaction. We consider the classical limit first, finding that the singly charged rings possess antiferroelectric order at low temperatures when the charge is discrete, but that they do not order when the charge is treated as a continuous classical fluid. In the quantum limit Monte Carlo simulation suggests that the system undergoes a quantum phase transition as the interaction strength is increased. This is supported by mapping the system to the 1D transverse field Ising model. Finally we examine the effect of magnetic fields. We find that a magnetic field can alter the electrostatic phase transition producing a ferroelectric groundstate, solely through its effect of shifting the eigenenergies of the quantum problem.Comment: 12 pages in two column format, 18 figure

Ambient air quality standards and policies in eastern mediterranean countries: a review

Objectives: National ambient air quality standards (NAAQS) are critical tools for controlling air pollution and protecting public health. We designed this study to 1) gather the NAAQS for six classical air pollutants: PM(2.5), PM(10), O(3), NO(2), SO(2), and CO in the Eastern Mediterranean Region (EMR) countries, 2) compare those with the updated World Health Organizations Air Quality Guidelines (WHO AQGs 2021), 3) estimate the potential health benefits of achieving annual PM(2.5) NAAQS and WHO AQGs per country, and 4) gather the information on air quality policies and action plans in the EMR countries. Methods: To gather information on the NAAQS, we searched several bibliographic databases, hand-searched the relevant papers and reports, and analysed unpublished data on NAAQS in the EMR countries reported from these countries to the WHO/Regional office of the Eastern Mediterranean/Climate Change, Health and Environment Unit (WHO/EMR/CHE). To estimate the potential health benefits of reaching the NAAQS and AQG levels for PM(2.5), we used the average of ambient PM(2.5) exposures in the 22 EMR countries in 2019 from the Global Burden of Disease (GBD) dataset and AirQ+ software. Results: Almost all of the EMR countries have national ambient air quality standards for the critical air pollutants except Djibouti, Somalia, and Yemen. However, the current standards for PM(2.5) are up to 10 times higher than the current health-based WHO AQGs. The standards for other considered pollutants exceed AQGs as well. We estimated that the reduction of annual mean PM(2.5) exposure level to the AQG level (5 mug m(-3)) would be associated with a decrease of all natural-cause mortality in adults (age 30+) by 16.9%-42.1% in various EMR countries. All countries would even benefit from the achievement of the Interim Target-2 (25 mug m(-3)) for annual mean PM(2.5): it would reduce all-cause mortality by 3%-37.5%. Less than half of the countries in the Region reported having policies relevant to air quality management, in particular addressing pollution related to sand and desert storms (SDS) such as enhancing the implementation of sustainable land management practices, taking measures to prevent and control the main factors of SDS, and developing early warning systems as tools to combat SDS. Few countries conduct studies on the health effects of air pollution or on a contribution of SDS to pollution levels. Information from air quality monitoring is available for 13 out of the 22 EMR countries. Conclusion: Improvement of air quality management, including international collaboration and prioritization of SDS, supported by an update (or establishment) of NAAQSs and enhanced air quality monitoring are essential elements for reduction of air pollution and its health effects in the EMR

A novel technique for detoxification of phenol from wastewater: Nanoparticle Assisted Nano Filtration (NANF)

© 2016 Naidu et al. Background: Phenol is one of the most versatile and important organic compound. It is also a growing concern as water pollutants due to its high persistence and toxicity. Removal of Phenol from wastewaters was investigated using a novel nanoparticle adsorption and nanofiltration technique named as Nanoparticle Assisted Nano Filtration (NANF). Methods: The nanoparticle used for NANF study were silver nanoparticles and synthesized to three distinct average particle sizes of 10 nm, 40 nm and 70 nm. The effect of nanoparticle size, their concentrations and their tri and diparticle combinations upon phenol removal were studied. Results: Total surface areas (TSA) for various particle size and concentrations have been calculated and the highest was 4710 × 1012 nm2 for 10 nm particles and 180 ppm concentration while the lowest was for 2461 × 1011 for 70 nm and 60 ppm concentrations. Tri and diparticle studies showed more phenol removal % than that of their individual particles, particularly for using small particles on large membrane pore size and large particles at low concentrations. These results have also been confirmed with COD and toxicity removal studies. Conclusions: The combination of nanoparticles adsorption and nanofiltration results in high phenol removal and mineralization, leading to the conclusion that NANF has very high potential for treating toxic chemical wastewaters

Graphene Bilayer Structures with Superfluid Magnetoexcitons

We study superfluid behavior of a gas of spatially indirect magnetoexcitons with reference to a system of two graphene layers embedded in a multilayer dielectric structure. The system is considered as an alternative of a double quantum well in a GaAs haterostructure. We determine a range of parameters (interlayer distance, dielectric constant, magnetic field and gate voltage) where magnetoexciton superfluidity can be achieved. Temperature of superfluid transition is computed. A reduction of critical parameters caused by impurities is evaluated and critical impurity concentration is determined

Study of the effect of MMC on the sister chromatid exchange in the human lymphocytes

Some environmental mutagenic agents cause genomic instability and increase susceptibility of DNA damage. One of them is mitomycin C which is connected to DNA as an alkylating factor and affects susceptible cells to reduction reactions. This drug is used in chemotherapy and treatment of tumors. Study of genomic instability in the presence of different concentrations of MMC can show susceptibility of DNA damage in the patients who are under chemotherapy with this drug. For this purpose, SCE is a qualified method that shows the number of sister chromatid exchanges in the metaphasic chromosomes. The number of 10^5 lymphocytic cells which were separated with ficol, were cultured in media (5ml, F12 15%-20% FCS) that contains mitogen of PHA (Phytohemagglutinin) and MMC in the concentrations of 3 ng/ml, 6 ng/ml and 9 ng/ml and a control sample without MMC. The specific concentration of BrdU was added after 24 hours to cell cultures. Then metaphasic cells were halted in the metaphasic stage with colchicine after 48 hours and were stained with SCE method and were studied for the number of sister chromatid exchanges in each metaphasic plaques. Evaluation of 100 metaphasic plates showed that SCE was 3.35% in the control cells while it was 5.43%, 7.1% and 8.13% in the treated cells with MMC in the concentrations of 3 ng/ml, 6 ng/ml and 9 ng/ml. In view of the results, it is clear than MMC can causes genomic instability even in the low concentrations and it can increase SCE so that the level of SCE is become the most with the concentration of 9 ng/ml and the least with the concentration of 3 ng/ml. In view of relation between SCE and DNA damage, we can conclude that the genome of normal cells will be damaged in the presence of MMC and in the patients who are under chemotherapy with this drug. It means that the genome of cells will become sensitive to mutation in the presence of low concentrations of MMC. Therefore we can postulate that we should use the concentrations of less than 3 ng/ml in order to decrease mutagenic effects of MMC in normal cells. Keywords: MMC, SCE, Cancer, Sister chromatid exchang

2D Shuttle Graphene Oxide and MXene Systems for Enhancing the Performance of Composite Cu2O/TiO2 Nanotube Photocatalysts

SSCI-VIDE+CARE+GBE:FDA:ZRS:CGUInternational audienceAddition of 2D conductive materials like graphene oxide (GO) or MXene sheets was herein demonstrated as an efficient way to separate physically electrons and holes in a composite photocatalytic system comprising TiO2 nanotubes on one side and Cu2O nanoparticles on the other side. Contrary to GO/TiO2 for which the GO overreduction under photocatalytic conditions leads to a complete loss of beneficial effect from GO, the use of two semiconductors Cu2O and TiO2 nanotubes separated physically by GO acting here as an electron-conductive 2D “shuttle” for electrons helps both to achieve a higher stability under photocatalytic conditions and a better separation of electrons and holes resulting in highly active photocatalytic systems

2D Shuttle Graphene Oxide and MXene Systems for Enhancing the Performance of Composite Cu2O/TiO2 Nanotube Photocatalysts

SSCI-VIDE+CARE+GBE:FDA:ZRS:CGUInternational audienceAddition of 2D conductive materials like graphene oxide (GO) or MXene sheets was herein demonstrated as an efficient way to separate physically electrons and holes in a composite photocatalytic system comprising TiO2 nanotubes on one side and Cu2O nanoparticles on the other side. Contrary to GO/TiO2 for which the GO overreduction under photocatalytic conditions leads to a complete loss of beneficial effect from GO, the use of two semiconductors Cu2O and TiO2 nanotubes separated physically by GO acting here as an electron-conductive 2D “shuttle” for electrons helps both to achieve a higher stability under photocatalytic conditions and a better separation of electrons and holes resulting in highly active photocatalytic systems