4,744 research outputs found

    Magnetic monolayer Li2_{2}N: Density Functional Theory Calculations

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    Density functional theory (DFT) calculations are used to investigate the electronic and magnetic structures of a two-dimensional (2D) monolayer Li2_{2}N. It is shown that bulk Li3_{3}N is a non-magnetic semiconductor. The non-spinpolarized DFT calculations show that pp electrons of N in 2D Li2_{2}N form a narrow band at the Fermi energy EFE_{\rm{F}} due to a low coordination number, and the density of states at the Fermi energy (g(EFg(E_{\rm{F}})) is increased as compared with bulk Li3_{3}N. The large g(EFg(E_{\rm{F}}) shows instability towards magnetism in Stoner's mean field model. The spin-polarized calculations reveal that 2D Li2_{2}N is magnetic without intrinsic or impurity defects. The magnetic moment of 1.0\,ÎĽB\mu_{\rm{B}} in 2D Li2_{2}N is mainly contributed by the pzp_{z} electrons of N, and the band structure shows half-metallic behavior. {Dynamic instability in planar Li2_{2}N monolayer is observed, but a buckled Li2_{2}N monolayer is found to be dynamically stable.} The ferromagnetic (FM) and antiferromagnetic (AFM) coupling between the N atoms is also investigated to access the exchange field strength. {We found that planar (buckled) 2D Li2_{2}N is a ferromagnetic material with Curie temperature TcT_{c} of 161 (572) K.}Comment: Euro Phys. Lett. 2017 (Accepted

    Iron(III)-catalyzed chlorination of activated arenes

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    A general and regioselective method for the chlorination of activated arenes has been developed. The transformation uses iron(III) triflimide as a powerful Lewis acid for the activation of N-chlorosuccinimide and the subsequent chlorination of a wide range of anisole, aniline, acetanilide and phenol derivatives. The reaction was utilized for the late-stage mono- and di-chlorination of a range of target compounds such as the natural product nitrofungin, the antibacterial agent chloroxylenol and the herbicide chloroxynil. The facile nature of this transformation was demonstrated with the development of one-pot tandem iron-catalyzed dihalogenation processes allowing highly regioselective formation of different carbon-halogen bonds. The synthetic utility of the resulting dihalogenated aryl compounds as building blocks was established with the synthesis of natural products and pharmaceutically relevant targets

    Dirac versus Reduced Quantization of the Poincar\'{e} Symmetry in Scalar Electrodynamics

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    The generators of the Poincar\'{e} symmetry of scalar electrodynamics are quantized in the functional Schr\"{o}dinger representation. We show that the factor ordering which corresponds to (minimal) Dirac quantization preserves the Poincar\'{e} algebra, but (minimal) reduced quantization does not. In the latter, there is a van Hove anomaly in the boost-boost commutator, which we evaluate explicitly to lowest order in a heat kernel expansion using zeta function regularization. We illuminate the crucial role played by the gauge orbit volume element in the analysis. Our results demonstrate that preservation of extra symmetries at the quantum level is sometimes a useful criterion to select between inequivalent, but nevertheless self-consistent, quantization schemes.Comment: 24 page

    Investigating the Impacts of Cyber-Attacks on Pricing Data of Home Energy Management Systems in Demand Response Programs

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    © 2018 IEEE. Provision of security involves protecting lives and properties, and properties in this context include data and services. This paper investigates the impact of cyber-attacks on load scheduling applications by simulating various possible modes for these attacks while observing possible effects on the users. The attack modes used are in the form of denial of service (DoS) and phishing attacks whereby the attacker is able to interfere with data intake to the Home Energy Management Systems (HEMS) or a modification of critical data to the HEMS. The dynamic pricing information and load profile data is the target here although other types of data utilized by the central controller for load scheduling purposes can also be targeted. The test-bed uses load scheduling applications based on genetic algorithm optimization. Results show the impact on optimized load profiles and how they can discourage active demand response participation if such attacks are not properly managed.Published versio

    Determination of gamma-ray widths in 15^{15}N using nuclear resonance fluorescence

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    The stable nucleus 15^{15}N is the mirror of 15^{15}O, the bottleneck in the hydrogen burning CNO cycle. Most of the 15^{15}N level widths below the proton emission threshold are known from just one nuclear resonance fluorescence (NRF) measurement, with limited precision in some cases. A recent experiment with the AGATA demonstrator array determined level lifetimes using the Doppler Shift Attenuation Method (DSAM) in 15^{15}O. As a reference and for testing the method, level lifetimes in 15^{15}N have also been determined in the same experiment. The latest compilation of 15^{15}N level properties dates back to 1991. The limited precision in some cases in the compilation calls for a new measurement in order to enable a comparison to the AGATA demonstrator data. The widths of several 15^{15}N levels have been studied with the NRF method. The solid nitrogen compounds enriched in 15^{15}N have been irradiated with bremsstrahlung. The Îł\gamma-rays following the deexcitation of the excited nuclear levels were detected with four HPGe detectors. Integrated photon-scattering cross sections of ten levels below the proton emission threshold have been measured. Partial gamma-ray widths of ground-state transitions were deduced and compared to the literature. The photon scattering cross sections of two levels above the proton emission threshold, but still below other particle emission energies have also been measured, and proton resonance strengths and proton widths were deduced. Gamma and proton widths consistent with the literature values were obtained, but with greatly improved precision.Comment: Final published version, minor grammar changes, 10 pages, 4 figures, 8 tables; An addendum is published where the last section is revised: T. Sz\"ucs and P. Mohr, Phys. Rev. C 92, 044328 (2015) [arXiv:1510.04956

    Cholate Conjugated Polymeric Amphiphiles as Efficient Artificial Ionophores

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    A family of amphiphilic copolymers containing hydrophobic cholate pendants has been prepared by copolymerization of cholic acid-based monomer 2-(methacryloxy)-ethyl cholate (MAECA) with polyethylene glycol methyl ether methacrylate (PEGMA). The polymers differ for the content of MAECA that increases from 0 to 35%. The copolymers partition within liposomes and display potent ionophoric activity forming large pores in the membrane and allowing the leakage of small inorganic ions (H+, Na+) and of large polar organic molecules (calcein). Their activity is strictly correlated to the content of cholic acid subunits, increasing as the fraction of cholate moiety increases

    Qualitative analysis of essential oil of Rosmarinus officinalis L. cultivated in Uttaranchal Hills, India

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    Gas chromatography and gas chromatography and mass spectroscopy analysis of essentialoil hydrodistilled from fresh aerial part of rosemary (Rosmarinus officinalis) cultivated inUttaranchal, India, resolved into 33 compounds representing 96.29% of the essential oilaccording to their chromatographic retention indices and mass spectra.  The major compoundsof the oil were, camphor (26.40%), 1, 8-cineole (23.40%), α-pinene (9.94%), camphene (5.83%),myrcene (4.86%), bornyl acetate (3.97%), verbenone (3.32%), limonene (3.08%), borneol(2.05%) and α-terpineol (2.68%). &nbsp

    Effect of plant growth regulators and activated charcoal on in vitro growth and development of oil palm (Elaeis guineensis Jacq. var. Dura) zygotic embryo

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    The effect of plant growth regulators and activated charcoal (AC) on in vitro regeneration and plantlet development of oil palm (Elaeis guineensis Jacq. var. Dura) zygotic embryos were assessed. Zygotic embryos were cultured on Murashige and Skoog (MS) medium supplemented with a blend of 0.05 or 0.1 mg/L of each plant growth regulators (PGR) (gibberellic acid, 6-benzlaminopurine and α-naphthaleneacetic acid) without or with 2 g/L AC. The growth and development of the embryos were affected by the types of media formulations. Zygotic embryos cultured on MS medium supplemented with both PGR and AC enhanced shoot initiation and subsequent plantlet development, while PGR supplemented MS media without AC led to abnormal growth, suggesting that AC is indispensable for oil palm plantlet regeneration in vitro. The best medium for growth and development of plantlets was MS medium supplemented with 0.1 mg/L PGR and 2 g/L AC which significantly increased plantlet height (9.4 cm) as well as root length (4.4 cm) than the remaining media formulations.Key words: Activated charcoal, oil palm, plant growth regulators, zygotic embryo

    A critical look at studies applying over-sampling on the TPEHGDB dataset

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    Preterm birth is the leading cause of death among young children and has a large prevalence globally. Machine learning models, based on features extracted from clinical sources such as electronic patient files, yield promising results. In this study, we review similar studies that constructed predictive models based on a publicly available dataset, called the Term-Preterm EHG Database (TPEHGDB), which contains electrohysterogram signals on top of clinical data. These studies often report near-perfect prediction results, by applying over-sampling as a means of data augmentation. We reconstruct these results to show that they can only be achieved when data augmentation is applied on the entire dataset prior to partitioning into training and testing set. This results in (i) samples that are highly correlated to data points from the test set are introduced and added to the training set, and (ii) artificial samples that are highly correlated to points from the training set being added to the test set. Many previously reported results therefore carry little meaning in terms of the actual effectiveness of the model in making predictions on unseen data in a real-world setting. After focusing on the danger of applying over-sampling strategies before data partitioning, we present a realistic baseline for the TPEHGDB dataset and show how the predictive performance and clinical use can be improved by incorporating features from electrohysterogram sensors and by applying over-sampling on the training set
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