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Dipolarization

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https://read.qxmd.com/read/30776853/the-influence-of-stereoelectronic-effects-on-the-1-j-c-f-spin-spin-coupling-constant-in-fluorinated-heterocyclic-compounds
#1
Josué M Silla, Laize A F Andrade, Matheus P Freitas
The Perlin effect and its analog for fluorinated compounds (the fluorine Perlin-like effect) manifest on one-bond C-H (C-F for the fluorine Perlin-like effect) spin-spin coupling constants (SSCC´s) in six-membered rings. These effects can be useful to probe the stereochemistry (axial or equatorial) of the C-H and C-F bonds, respectively. The origin of these effects has been debatable in the literature as being due to hyperconjugative interactions, dipolar effects and induced current density. Accordingly, a variety of model compounds has been used to probe such effects, since the cyclohexanone carbonyl group and the endocyclic heteroatom lone pairs play different roles on the above-mentioned effects...
February 18, 2019: Magnetic Resonance in Chemistry: MRC
https://read.qxmd.com/read/30776244/hyperbolic-meta-antennas-enable-full-control-of-scattering-and-absorption-of-light
#2
Nicolò Maccaferri, Yingqi Zhao, Tommi Isoniemi, Marzia Iarossi, Antonietta Parracino, Giuseppe Strangi, Francesco De Angelis
We introduce a novel concept of hybrid metal-dielectric meta-antenna supporting type II hyperbolic dispersion, which enables a full control of absorption and scattering of light in the visible/near-infrared spectral range. This ability lies on the different nature of the hyperbolic Bloch-like modes excited within the meta-antenna. The experimental evidence is corroborated by a comprehensive theoretical study. In particular, we demonstrate that two main modes, one radiative and one non-radiative, can be excited by direct coupling with the free-space radiation...
February 18, 2019: Nano Letters
https://read.qxmd.com/read/30773581/probing-interactions-within-liquid-media-via-a-model-h-bond-donor-acceptor-mixture
#3
Anu Kadyan, Yashika Gandhi, Siddharth Pandey
Understanding interactions within liquids so as to obtain desired physicochemical properties is of utmost importance in chemistry. Solute-solvent and solvent-solvent interactions within mixtures of hexamethylphosphoramide (HMPA) and 2,2,2-trifluoroethanol (TFE) are assessed using various invasive and non-invasive techniques. HMPA and TFE possess similar static dielectric constants. While HMPA has high H-bond accepting basicity (β ∼ 1) and no H-bond donating acidity (α ∼ 0), TFE has high H-bond donating acidity (α ∼ 1) and almost no H-bond accepting basicity (β ∼ 0)...
February 18, 2019: Physical Chemistry Chemical Physics: PCCP
https://read.qxmd.com/read/30768351/probing-quantum-thermalization-of-a-disordered-dipolar-spin-ensemble-with-discrete-time-crystalline-order
#4
Joonhee Choi, Hengyun Zhou, Soonwon Choi, Renate Landig, Wen Wei Ho, Junichi Isoya, Fedor Jelezko, Shinobu Onoda, Hitoshi Sumiya, Dmitry A Abanin, Mikhail D Lukin
We investigate thermalization dynamics of a driven dipolar many-body quantum system through the stability of discrete time crystalline order. Using periodic driving of electronic spin impurities in diamond, we realize different types of interactions between spins and demonstrate experimentally that the interplay of disorder, driving, and interactions leads to several qualitatively distinct regimes of thermalization. For short driving periods, the observed dynamics are well described by an effective Hamiltonian which sensitively depends on interaction details...
February 1, 2019: Physical Review Letters
https://read.qxmd.com/read/30768276/ac-electrowetting-modulation-of-low-volatile-liquids-probed-by-xps-dipolar-vs-ionic-screening
#5
Pinar Aydogan Gokturk, Burak Ulgut, Sefik Suzer
X-ray photoelectron spectroscopic (XPS) data have been recorded from a low molecular weight polyethylene glycol (PEG) µl-sized sessile liquid drops sitting on a dielectric covered planar electrode, while imposing a ± 6V square-wave actuation with varying frequencies between 10-1 - 105 Hz to tap into the information derivable from AC Electrowetting. We show that this time-varying XPS spectra reveal two distinct behaviors of the device under investigation, below and above a critical frequency, measured as ~70 Hz for the liquid polyethylene glycol with a 600 Da molecular weight...
February 15, 2019: Langmuir: the ACS Journal of Surfaces and Colloids
https://read.qxmd.com/read/30768258/identification-of-boronic-acid-derivatives-as-an-active-form-of-n-alkylaminoferrocene-based-anticancer-prodrugs-and-their-radiolabeling-with-18f
#6
Steffen Daum, Johannes Toms, Viktor Reshetnikov, Gizem Hülya, Frank Hampel, Simone Maschauer, Amir H Hakimioun, Frank R Beierlein, Olaf Prante, Andriy Mokhir, Leopold Sellner, Michael Schmitt
N-Alkylaminoferrocene (NAAF)-based prodrugs are activated in the presence of elevated amounts of reactive oxygen species (ROS), that corresponds to cancer specific conditions, with formation of NAAF and p-quinone methide. These both products act synergistically by increasing oxidative stress in cancer cells that causes their death. Though it has been already demonstrated that the best prodrugs of this type retain their antitumor activity in vivo, the effects were found to be substantially weaker than those observed in cell cultures...
February 15, 2019: Bioconjugate Chemistry
https://read.qxmd.com/read/30768111/pentamethylcyclopentadienyl-osmium-complexes-that-contain-diazoalkane-dioxygen-and-allenylidene-ligands-preparation-and-reactivity
#7
Gabriele Albertin, Stefano Antoniutti, Jesús Castro, Francesca Sibilla
Diazoalkane complexes [Os(η5-C5Me5)(N2CAr1Ar2)(PPh3){P(OR)3}]BPh4 (1, 2) [R = Me (1), Et (2); Ar1 = Ar2 = Ph (a); Ar1 = Ph, Ar2 = p-tolyl (b); Ar1Ar2 = C12H8 (fluorenyl) (c)] were prepared by reacting bromo-compounds OsBr(η5-C5Me5)(PPh3){P(OR)3} with an excess of diazoalkane in ethanol. The treatment of diazoalkane complexes 1 and 2 with acetylene under mild conditions (1 atm, RT) led to dipolar (3 + 2) cycloaddition affording 3H-pyrazole derivatives [Os(η5-C5Me5)(η1-[upper bond 1 start]N[double bond, length as m-dash]NC(C12H8)CH[double bond, length as m-dash]C[upper bond 1 end]H)(PPh3){P(OR)3}]BPh4 (6, 7) [R = Me (6), Et (7)] whereas reactions with terminal alkynes R1C[triple bond, length as m-dash]CH (R1 = Ph, p-tolyl, COOMe) gave vinylidene derivatives [Os(η5-C5Me5){[double bond, length as m-dash]C[double bond, length as m-dash]C(H)R1}(PPh3){P(OR)3}]BPh4 (8b-d, 9b-d) [R = Me (8), Et (9); R1 = Ph (b), p-tolyl (c), COOMe (d)]...
February 15, 2019: Dalton Transactions: An International Journal of Inorganic Chemistry
https://read.qxmd.com/read/30768099/%C3%AE-%C3%AE-unsaturated-butenolides-in-an-organocatalytic-doubly-annulative-cascade-for-the-preparation-of-3-4-dihydrocoumarins
#8
Dorota Kowalczyk-Dworak, Łukasz Albrecht
A new, organocatalytic doubly annulative cascade utilizing α,β-unsaturated butenolides and imines (derived from salicyl aldehydes and α-amino-γ-lactones) as starting materials is described. The developed strategy is based on two annulative processes: (1) initial [3 + 2]-dipolar cycloaddition allowing for the construction of a pyrrolidine ring; and (2) the butenolide-ring-opening reaction leading to the introduction of a 3,4-dihydrocoumarin framework. Target polycyclic compounds have been obtained with excellent chemical and stereochemical efficiencies...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30762361/uncommon-polyoxygenated-sesquiterpenoids-from-south-china-sea-soft-coral-lemnalia-flava
#9
Qihao Wu, Fei Ye, Xiao-Lu Li, Lin-Fu Liang, Jiadong Sun, Han Sun, Yue-Wei Guo, Hong Wang
A detailed chemical investigation of the Chinese soft coral Lemnalia flava yielded four new nardosinane-type sesquiterpenoids (1-4), one new neolemnane-type sesquiterpenoid (5), and one new sesquiterpenoid with an uncommon 6/9 fused bicyclic skeleton (6), along with two known related compounds (7-8). The structures and absolute configurations of 1-8 were determined on the basis of extensive spectroscopic data analysis, X-ray diffraction analysis, chemical reactions and computer-assisted structural elucidation including 13C NMR data calculation, residual dipolar coupling (RDC) based NMR analysis, and TDDFT-ECD calculation...
February 14, 2019: Journal of Organic Chemistry
https://read.qxmd.com/read/30762170/alpha-protons-as-nmr-probes-in-deuterated-proteins
#10
Kumar Tekwani Movellan, Eszter E Najbauer, Supriya Pratihar, Michele Salvi, Karin Giller, Stefan Becker, Loren B Andreas
We describe a new labeling method that allows for full protonation at the backbone Hα position, maintaining protein side chains with a high level of deuteration. We refer to the method as alpha proton exchange by transamination (α-PET) since it relies on transaminase activity demonstrated here using Escherichia coli expression. We show that α-PET labeling is particularly useful in improving structural characterization of solid proteins by introduction of an additional proton reporter, while eliminating many strong dipolar couplings...
February 14, 2019: Journal of Biomolecular NMR
https://read.qxmd.com/read/30762054/charge-polarization-near-dielectric-interfaces-and-the-multiple-scattering-formalism
#11
REVIEW
Jian Qin
Interfacial charge polarization is ubiquitous in systems with sharp dielectric contrast. Fully resolving the interfacial charges often relies on demanding numerical algorithms to solve the boundary value problem. The recent development of an analytical multiple-scattering formalism to solve the interfacial charge polarization problem for particles carrying monopolar, dipolar, and multipolar charges is reviewed. Every term produced in this formalism has a simple interpretation, and terms for spherical particles can be rapidly evaluated using an image-line construction...
February 14, 2019: Soft Matter
https://read.qxmd.com/read/30753912/fastigial-nucleus-electrostimulation-promotes-axonal-regeneration-after-experimental-stroke-via-camp-pka-pathway
#12
An-Rong Wang, Ming-Zhe Hu, Zhi-Lei Zhang, Ze-Yu Zhao, Yan-Bin Li, Bin Liu
Axon regeneration after cerebral ischemia in mammals is inadequate to restore function, illustrating the need to design better strategies for improving outcomes. Improvement of axon regeneration has been achieved through fastigial nucleus electrostimulation (FNS) in animal researches. However, the mechanisms underlying this neuroprotection remain poorly understood. Increasing the levels of the second messenger cyclic AMP (cAMP) enhances axon regeneration, making it an excellent candidate molecule that has therapeutic potential...
February 10, 2019: Neuroscience Letters
https://read.qxmd.com/read/30747536/tfa-mediated-dmso-participant-sequential-oxidation-1-3-dipolar-cycloaddition-cascade-of-pyridinium-ylides-for-the-assembly-of-indolizines
#13
Wen-Ming Shu, Jian-Xin He, Xun-Fang Zhang, Shuai Wang, An-Xin Wu
A trifluoroacetic acid (TFA)-mediated cascade oxidation/1,3-dipolar cycloaddition reaction of stabilized pyridinium salts with dimethyl sulfoxide (DMSO) has been developed in the presence of K2 S2 O8 and trimethylethylenediamine (TMEDA). In this transition-metal-free reaction, DMSO acts as a one-carbon source, thus providing a convenient method for the efficient and direct synthesis of various indolizine derivatives.
February 12, 2019: Journal of Organic Chemistry
https://read.qxmd.com/read/30744756/novel-drug-delivery-system-based-on-ginsenoside-rb1-loaded-to-chitosan-alginate-nanocomposite-films
#14
Thai Hoang, Kavitha Ramadass, Thach Thi Loc, Tran Thi Mai, Le Duc Giang, Vu Viet Thang, Tran Minh Tuan, Nguyen Thuy Chinh
Recently, drug delivery using natural and biodegradable nanoparticles has attracted huge attention. This study focused to deliver an anti-cancer and anti-inflammatory drug Ginsenoside Rb1 through chitosan-Alginate nanocomposite film prepared by solution method. Ginsenoside Rb1 is a dammaran saponin group, which is extracted from an herbaceous plant Panax notoginseng . Ginsenoside loaded alginate-chitosan nanocomposite films were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) methods...
June 1, 2019: Journal of Nanoscience and Nanotechnology
https://read.qxmd.com/read/30743071/ftir-and-dispersive-gas-phase-absolute-infrared-intensities-of-hydrocarbon-fundamental-bands
#15
Leonardo J Duarte, Roy E Bruns
New experimental intensity results obtained by band integration from the PNNL (Pacific Northwest National Laboratory) spectral library are reported for 26 CH vibrations of methane, acetylene, ethylene, ethane, allene, propyne and cyclopropane. The PNNL intensity values range from 3.1 to 185.4 km mol-1 and are in excellent agreement, rms difference of 3.1 km mol-1 , with earlier low resolution intensity results. QCISD/6-311++G(3d,3p) and QCISD/cc-pVTZ theoretical results are in good agreement with the PNNL intensity values with rms differences of 4...
January 25, 2019: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://read.qxmd.com/read/30735578/reducing-the-computational-cost-of-nmr-crystallography-of-organic-powders-at-natural-isotopic-abundance-with-the-help-of-13-c-13-c-dipolar-couplings
#16
Pierre Thureau, Simone Sturniolo, Miri Zilka, Fabio Ziarelli, Stéphane Viel, Jonathan Yates, Giulia Mollica
Structure determination of functional organic compounds remains a formidable challenge when the sample exists as a powder. NMR crystallography approaches based on the comparison of experimental and DFT-computed 1H chemical shifts have already demonstrated great potential for structure determination of organic powders, but limitations still persist. In this study we discuss the possibility of using 13C-13C dipolar couplings quantified on powdered theophylline at natural isotopic abundance with the help of dynamic nuclear polarisation, to realize a DFT-free, rapid, screening of a pool of structures predicted by AIRSS...
February 8, 2019: Magnetic Resonance in Chemistry: MRC
https://read.qxmd.com/read/30732315/realization-of-switchable-eit-metamaterial-by-exploiting-fluidity-of-liquid-metal
#17
Jing Xu, Yuancheng Fan, Ruisheng Yang, Quanhong Fu, Fuli Zhang
Novel manipulation techniques for the propagation of electromagnetic waves based on metamaterials can only be performed in narrow operating bands, and this drawback is a major challenge for developing metamaterial-based practical applications. We demonstrate that the scattering of metamaterials can be switched and that their operating band can be tuned by introducing liquid metal in the design of functional metamaterials. The proposed liquid metal-based metamaterial is composed of a copper wire pair and a tiny pipe filled with a liquid metal, namely eutectic gallium-indium...
February 4, 2019: Optics Express
https://read.qxmd.com/read/30720277/sarcomililate-a-an-unusual-diterpenoid-with-tricyclo-11-3-0-0-2-16-hexadecane-carbon-skeleton-and-its-potential-biogenetic-precursors-from-the-hainan-soft-coral-sarcophyton-mililatensis
#18
Min Yang, Xiao-Lu Li, Jian-Rong Wang, Xinxiang Lei, Wei Tang, Xu-Wen Li, Han Sun, Yue-Wei Guo
A novel diterpenoid, sarcomililate A (1), possessing a previously undescribed tricyclo[11.3.0.02,16 ]hexadecane scaffold, along with two new cembranoids, sarcomililatols A and B (2 and 3), two known related diterpenoids (4 and 5) were isolated from the Hainan soft coral Sarcophyton mililatensis. The complete chemical structure including absolute configuration (AC) of 1 was unambiguously determined by a combination of residual dipolar coupling (RDC) based NMR analysis, TDDFT-ECD calculation, and Snatzke's method...
February 5, 2019: Journal of Organic Chemistry
https://read.qxmd.com/read/30718657/improved-configuration-and-lspr-response-of-platinum-nanoparticles-via-enhanced-solid-state-dewetting-of-in-pt-bilayers
#19
Sundar Kunwar, Mao Sui, Puran Pandey, Zenan Gu, Sanchaya Pandit, Jihoon Lee
Noble metallic nanoparticles (NPs) can exhibit valuable properties such as localized surface plasmon resonance (LSPR) and large surface to volume ratio, which can find various optoelectronic and catalytic applications. In this work, the improved configuration and uniformity of platinum (Pt) NPs are demonstrated by using a sacrificial indium (In) layer via the enhanced solid state dewetting of In-Pt bilayers on sapphire (0001). In a sharp contrast to the conventional dewetting of intrinsic Pt film, the introduction of In component can significantly enhance the global dewetting process and thus can result in the fabrication of well-defined Pt NPs with the improved uniformity...
February 4, 2019: Scientific Reports
https://read.qxmd.com/read/30717591/europium-cyclooctatetraene-nanowire-carpets-a-low-dimensional-organometallic-and-ferromagnetic-insulator
#20
Felix Huttmann, Nico Rothenbach, Stefan Kraus, Katharina Ollefs, Lucas M Arruda, Matthias Bernien, Danny Thonig, Anna Delin, Jonas Fransson, Kurt Kummer, Nicholas B Brookes, Olle Eriksson, Wolfgang Kuch, Thomas Michely, Heiko Wende
We investigate the magnetic and electronic properties of europium cyclooctatetraene nanowires (EuCot) by means of low-temperature x-ray magnetic circular dichroism (XMCD) and scanning tunneling microscopy (STM) and spectroscopy (STS). The EuCot nanowires are prepared in situ on a graphene surface. STS measurements identify EuCot as a wide-band-gap semiconductor with a band gap of 2.3 eV. By means of Eu M5,4 edge XMCD, orbital and spin magnetic moments of (-0.1 ±0.3) μΒ and (+7.0 ±0.6) μΒ , respectively, were determined...
February 4, 2019: Journal of Physical Chemistry Letters
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