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https://www.readbyqxmd.com/read/29334685/observation-of-a-phononic-quadrupole-topological-insulator
#1
Marc Serra-Garcia, Valerio Peri, Roman Süsstrunk, Osama R Bilal, Tom Larsen, Luis Guillermo Villanueva, Sebastian D Huber
The modern theory of charge polarization in solids is based on a generalization of Berry's phase. The possibility of the quantization of this phase arising from parallel transport in momentum space is essential to our understanding of systems with topological band structures. Although based on the concept of charge polarization, this same theory can also be used to characterize the Bloch bands of neutral bosonic systems such as photonic or phononic crystals. The theory of this quantized polarization has recently been extended from the dipole moment to higher multipole moments...
January 15, 2018: Nature
https://www.readbyqxmd.com/read/29334394/substitution-of-the-laser-borane-anti-b18h22-with-pyridine-a-structural-and-photophysical-study-of-some-unusually-structured-macropolyhedral-boron-hydrides
#2
Michael G S Londesborough, Jiří Dolanský, Tomáš Jelínek, John D Kennedy, Ivana Císařová, Robert D Kennedy, Daniel Roca-Sanjuán, Antonio Francés-Monerris, Kamil Lang, William Clegg
Reaction of anti-B18H221 with pyridine in neutral solvents gives sparingly soluble B16H18-3',8'-Py23a as the major product (ca. 53%) and B18H20-6',9'-Py22 (ca. 15%) as the minor product, with small quantities of B18H20-8'-Py 4 (ca. 1%) also being formed. The three new compounds 2, 3a and 4 are characterized by single-crystal X-ray diffraction analyses and by multinuclear multiple-resonance NMR spectroscopy. Compound 2 is of ten-vertex nido:ten-vertex arachno two-atoms-in-common architecture, long postulated for a species with borons-only cluster constitution, but previously elusive...
January 15, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29334361/engineering-the-spin-polarization-of-one-dimensional-electrons
#3
Chengyu Yan, Sanjeev Kumar, Kalarikad Thomas, Patrick See, Ian Farrer, David A Ritchie, John Griffiths, G A C Jones, Michael Pepper
We present results of magneto-focusing on the controlled monitoring of spin polarization within a one-dimensional (1D) channel, and its subsequent effect on modulating the spin-orbit interaction (SOI) in a 2D GaAs electron gas. We demonstrate that electrons within a 1D channel can be partially spin polarized as the effective length of the 1D channel is varied in agreement with the theoretical prediction. Such polarized 1D electrons when injected into a 2D region result in a split in the odd-focusing peaks, whereas the even peaks remain unaffected (single peak)...
January 15, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/29334335/simultaneous-formation-of-polycyclic-aromatic-hydrocarbons-pahs-and-heterocyclic-aromatic-amines-hcas-in-gas-grilled-beef-satay-at-different-temperatures
#4
A K Nor Hasyimah, S Jinap, M Sanny
This study investigated the simultaneous formation of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HCAs) in gas-grilled beef satay at different temperatures (150°C, 200°C, 250°C, 300°C, and 350°C). Solid-phase extraction (SPE) was used for sample clean-up. Fifteen PAHs were determined using high performance liquid chromatography with fluorescence detection (HPLC-FLD) and nine HCAs were quantified using liquid chromatography tandem-mass spectrometry (LC-MS/MS) with a gradient programme...
January 15, 2018: Food Additives & Contaminants. Part A, Chemistry, Analysis, Control, Exposure & Risk Assessment
https://www.readbyqxmd.com/read/29334125/determination-of-isoorientin-levels-in-rat-plasma-after-oral-administration-of-vaccinum-bracteatum-thunb-methanol-extract-by-high-performance-liquid-chromatography-tandem-mass-spectrometry
#5
Min-Ji Kim, Seung-Hwan Kwon, Choon-Gon Jang, Han-Joo Maeng
A simple, sensitive and rapid liquid chromatography tandem mass spectrometry method (LC-MS/MS) was developed and validated for the determination of plasma isoorientin levels in rats. After simple protein precipitation using methanol, chromatographic analysis was performed using a Synergi 4μ polar-RP 80A column (150 mm × 2.0 mm, 4 μm) under isocratic conditions and a mobile phase consisting of 0.1% formic acid in water and methanol (80:20, v/v) at a flow rate of 0.2 mL/min. In positive electrospray ionization mode, the protonated precursor and product ion transitions of isoorientin (m/z 449...
January 15, 2018: Biomedical Chromatography: BMC
https://www.readbyqxmd.com/read/29334087/achiral-non-fluorescent-molecule-assisted-enhancement-of-circularly-polarized-luminescence-in-naphthalene-substituted-histidine-organogels
#6
Dian Niu, Lukang Ji, Guanghui Ouyang, Minghua Liu
A naphthalene substituted histidine derivative was found to form an organogel showing circularly polarized luminescence (CPL) and the addition of non-fluorescent achiral benzoic acids could efficiently enhance the CPL via non-covalent interactions.
January 15, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29333991/evaluation-of-a-portable-gas-chromatograph-with-photoionization-detector-under-variations-of-voc-concentration-temperature-and-relative-humidity
#7
Jhy-Charm Soo, Eun Gyung Lee, Ryan F LeBouf, Michael L Kashon, William Chisholm, Martin Harper
The objective of this present study was to evaluate the performance of a portable gas chromatograph ─ photoionization detector (GC-PID), under various test conditions to determine if it could be used in occupational settings. A mixture of seven volatile organic compounds (VOCs) - acetone, ethylbenzene, methyl isobutyl ketone, toluene, m-xylene, p-xylene, and o-xylene - was selected because its components are commonly present in paint manufacturing industries. A full-factorial combination of four concentration levels (exposure scenarios) of VOC mixtures, three different temperatures (25˚C, 30˚C, and 35˚C), and three relative humidities (RHs; 25%, 50%, and 75%) was conducted in a full- size controlled environmental chamber...
January 15, 2018: Journal of Occupational and Environmental Hygiene
https://www.readbyqxmd.com/read/29333630/efficient-supercapacitor-energy-storage-using-conjugated-microporous-polymer-networks-synthesized-from-buchwald-hartwig-coupling
#8
Yaozu Liao, Haige Wang, Meifang Zhu, Arne Thomas
Supercapacitors have received increasing interest as energy storage devices due to their rapid charge-discharge rates, high power densities, and high durability. In this work, novel conjugated microporous polymer (CMP) networks are presented for supercapacitor energy storage, namely 3D polyaminoanthraquinone (PAQ) networks synthesized via Buchwald-Hartwig coupling between 2,6-diaminoanthraquinone and aryl bromides. PAQs exhibit surface areas up to 600 m2 g-1 , good dispersibility in polar solvents, and can be processed to flexible electrodes...
January 15, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29333628/re-bpy-co-3cl-immobilized-on-bipyridine-periodic-mesoporous-organosilica-for-photocatalytic-co2-reduction
#9
Minoru Waki, Ken-Ichi Yamanaka, Soichi Shirai, Yoshifumi Maegawa, Yasutomo Goto, Yuri Yamada, Shinji Inagaki
This paper describes the physicochemical properties of a rhenium (Re) complex [Re(bpy)(CO)3Cl] immobilized on a bipyridine-periodic mesoporous organosilica (BPy-PMO) acting as a solid support. The immobilized Re complex generated a metal-to-ligand charge transfer absorption band at 400 nm. This wavelength is longer than that exhibited by Re(bpy)(CO)3Cl in the polar solvent acetonitrile (371 nm) and is almost equal to that in nonpolar toluene (403 nm). The photocatalytic activity of this heterogeneous Re complex was lower than that of a homogeneous Re complex due to the reduced phosphorescence lifetime resulting from immobilization...
January 14, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29333547/diverse-bimetallic-mechanisms-emerging-from-transition-metal-lewis-acid-base-pairs-development-of-co-catalysis-with-metal-carbenes-and-metal-carbonyl-anions
#10
Neal P Mankad
The rational development of catalytic reactions involving cooperative behavior between two catalytic reactive sites represents a frontier area of research from which novel reactivity and selectivity patterns emerge. Within this context, this Feature highlights the development of a cooperative system involving transition metal Lewis acid/base pairs. Bimetallic systems consisting of copper carbene Lewis acids and metal carbonyl anion Lewis bases, (NHC)Cu-[MCO], are easily synthesized from readily available organometallic building blocks (NHC = N-heterocyclic carbene; [MCO]- = metal carbonyl anion, e...
January 15, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29332384/structure-of-lipid-nanoparticles-containing-sirna-or-mrna-by-dynamic-nuclear-polarization-enhanced-nmr-spectroscopy
#11
Jasmine Viger-Gravel, Anna Schantz, Arthur C Pinon, Aaron J Rossini, Staffan Schantz, Lyndon Emsley
Here we show how dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy experiments permit the atomic level structural characterization of loaded and empty lipid nanoparticles (LNPs). The LNPs used here were synthesized by microfluidic mixing technique and are composed of ionizable cationic lipid (DLin-MC3-DMA), a phospholipid (DSPC), cholesterol and PEG (DMPE-PEG 2000), as well as encapsulated cargoes which are either phosphorothioated-siRNA (50 or 100%) or mRNA. We show that LNPs form physically stable complexes with bioactive drug siRNA for a period of 94 days...
January 14, 2018: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29331905/macrophage-phenotype-switch-by-sequential-action-of-immunomodulatory-cytokines-from-hydrogel-layers-on-titania-nanotubes
#12
Junhong Chen, Mengting Li, Congling Yang, Xianzhen Yin, Ke Duan, Jianxin Wang, Bo Feng
Inflammatory response occurring between tissues and implants after implantation has attracted increasing attention because it can cause local tissue necrosis and even implant failure. Macrophages play a key role in all stages of inflammation. Pro-inflammatory (M1) and anti-inflammatory (M2) macrophages comprise two main phenotypes and the switch from M1 to M2 at specific time points is important for wound healing and tissue regeneration. Therefore, we hypothesized that biomaterial systems capable of facilitating macrophage phenotype switching should attenuate inflammation and enhance healing...
January 9, 2018: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/29331814/characterization-of-sp3-bond-content-of-carbon-films-deposited-by-high-power-gas-injection-magnetron-sputtering-method-by-uv-and-vis-raman-spectroscopy
#13
Krzysztof Zdunek, Rafał Chodun, Bartosz Wicher, Katarzyna Nowakowska-Langier, Sebastian Okrasa
This paper presents the results of investigations of carbon films deposited by a modified version of the magnetron sputtering method - HiPGIMS (High Power Gas Injection Magnetron Sputtering). In this experiment, the magnetron system with inversely polarized electrodes (sputtered cathode at ground potential and positively biased, spatially separated anode) was used. This arrangement allowed us to conduct the experiment using voltages ranging from 1 to 2kV and a power supply system equipped with 25/50μF capacitor battery...
January 5, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/29331558/high-resolution-129i-bomb-peak-profile-in-an-ice-core-from-se-dome-site-greenland
#14
Angel T Bautista, Yasuto Miyake, Hiroyuki Matsuzaki, Yoshinori Iizuka, Kazuho Horiuchi
129I in natural archives, such as ice cores, can be used as a proxy for human nuclear activities, age marker, and environmental tracer. Currently, there is only one published record of 129I in ice core (i.e., from Fiescherhorn Glacier, Swiss Alps) and its limited time resolution (1-2 years) prevents the full use of 129I for the mentioned applications. Here we show 129I concentrations in an ice core from SE-Dome, Greenland, covering years 1956-1976 at a time resolution of ∼6 months, the most detailed record to date...
January 11, 2018: Journal of Environmental Radioactivity
https://www.readbyqxmd.com/read/29331518/microwave-assisted-ionic-liquid-mediated-rapid-catalytic-conversion-of-non-edible-lignocellulosic-sunn-hemp-fibres-to-biofuels
#15
Souvik Kumar Paul, Saikat Chakraborty
Sunn hemp fibre - a cellulose-rich crystalline non-food energy crop, containing 75.6% cellulose, 10.05% hemicellulose, 10.32% lignin, with high crystallinity (80.17%) and degree of polymerization (650) - is identified as a new non-food substrate for lignocellulosic biofuel production. Microwave irradiation is employed to rapidly rupture the cellulose's glycosidic bonds and enhance glucose yield to 78.7% at 160 °C in only 46 min. The reactants - long-chain cellulose, ionic liquid, transition metal catalyst, and water - form a polar supramolecular complex that rotates under the microwave's alternating polarity and rapidly dissipates the electromagnetic energy through molecular collisions, thus accelerating glycosidic bond breakage...
January 3, 2018: Bioresource Technology
https://www.readbyqxmd.com/read/29331439/interactions-of-dimethylaminoethyl-methacrylate-copolymer-with-non-acidic-drugs-demonstrated-high-solubilization-in-vitro-and-pronounced-sustained-release-in-vivo
#16
Wiebke Saal, Nicole Wyttenbach, Jochem Alsenz, Martin Kuentz
Recent work demonstrated remarkable solubilization effects of methacrylate-copolymer Eudragit EPO (EPO) not only with acidic drugs but interestingly also with poorly soluble basic compounds. The current work studied EPO-mediated solubilization effects first in vitro using felodipine (FLP) and tamoxifen (TMX) as model compounds. EPO-containing solutions were subsequently compared in a rat pharmacokinetic study against reference solutions and suspensions. Surprisingly, solution formulations with EPO did not result in an increased relative oral bioavailability...
January 10, 2018: European Journal of Pharmaceutics and Biopharmaceutics
https://www.readbyqxmd.com/read/29331370/preparation-and-evaluation-of-antibacterial-potential-of-pithecellobium-dulce-root-extract-against-gram-positive-and-gram-negative-bacteria
#17
Muneer Ahmad Bhat, Rayees Ahmad Malik, Poonam Prakash, Ali Mohd Lone
In the present study hexane, benzene, ethyl acetate and ethanol extracts of Pithecellobium dulce root were prepared using soxhlet extractor. The extracts were evaluated for antibacterial activity against one Gram positive (Staphylococcus aureus) and three Gram negative (Acetobacter aceti, Acetobacter aceti, Klebsiella pneumoniae) strains. Disc diffusion method revealed promising antibacterial activity of the extracts prepared in polar solvents (ethyl acetate and ethanol) compared to non-polar solvents (hexane and benzene)...
January 10, 2018: Microbial Pathogenesis
https://www.readbyqxmd.com/read/29331333/influences-of-conformations-of-peptides-on-stereoinversions-and-or-isomerizations-of-aspartic-acid-residues
#18
Akifumi Oda, Tomoki Nakayoshi, Shuichi Fukuyoshi, Eiji Kurimoto, Ohgi Takahashi
Recently, non-enzymatic stereoinversions of aspartic acid (Asp) residues in proteins and peptides have been reported. Here, we performed replica exchange molecular dynamics (REMD) simulations of model peptides (exon 6, 26A-1, and 26A-2) extracted from elastin to investigate their structural features, thereby revealing the factor that influences stereoinversions. For REMD trajectories, we calculated distances between carboxyl carbon in Asp and amide nitrogen in the (n + 1) residue (C-N distances). Because bond formation between carbon and nitrogen is indispensable to the formation of a succinimide intermediate the distance between them seems to play an important role in stereoinversion...
January 10, 2018: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/29331225/influence-of-pressure-on-the-retention-of-resorcinarene-based-cavitands
#19
Ibolya Prauda, Endre Bartó, Attila Felinger
The thermodynamics of the retention mechanism of resorcinarene-based cavitands in RPLC as well as the nature of the binding sites have been studied recently. In the present study, the influence of pressure on the retention of the cyclic tetramers on alkylsilyl and polar-embedded C8 and C18 stationary phases is investigated using aqueous methanol mobile phase. The pressure effect for cavity-shaped molecules has been scarcely studied so far. We observed that the retention factors of the analytes increased with the increase of the average column pressure (1-400 bar) when using restricting capillary tubes...
January 9, 2018: Journal of Chromatography. A
https://www.readbyqxmd.com/read/29331136/zwitterionization-of-glycine-in-water-environment-stabilization-mechanism-and-nmr-spectral-signatures
#20
Danillo Valverde, Zélia Maria da Costa Ludwig, Célia Regina da Costa, Valdemir Ludwig, Herbert C Georg
At physiological conditions, myriads of biomolecules (e.g., amino acids, peptides, and proteins) exist predominantly in the zwitterionic structural form and their biological functions will result in these conditions. However these geometrical structures are inaccessible energetically in the gas phase, and at this point, stabilization of amino-acids in physiological conditions is still under debate. In this paper, the electronic properties of a glycine molecule in the liquid environment were studied by performing a relaxation of the glycine geometry in liquid water using the free energy gradient method combined with a sequential quantum mechanics/molecular mechanics approach...
January 14, 2018: Journal of Chemical Physics
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