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https://www.readbyqxmd.com/read/29729484/high-efficiency-dual-cycle-conversion-system-using-kr-85
#1
Mark A Prelas, Modeste Tchakoua Tchouaso
This paper discusses the use of one of the safest isotopes known isotopes, Kr-85, as a candidate fuel source for deep space missions. This isotope comes from 0.286% of fission events. There is a vast quantity of Kr-85 stored in spent fuel and it is continually being produced by nuclear reactors. In using Kr-85 with a novel Dual Cycle Conversion System (DCCS) it is feasible to boost the system efficiency from 26% to 45% over a single cycle device while only increasing the system mass by less than 1%. The Kr-85 isotope is the ideal fuel for a Photon Intermediate Direct Energy Conversion (PIDEC) system...
April 26, 2018: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/29688716/synthesis-and-structure-of-sn-14-cl-6-ch-2-sime-3-12-toward-nanoclusters-of-4-coordinate-%C3%AE-sn
#2
Andrew P Purdy, Raymond J Butcher, James P Yesinowski, Sean A Fischer, Daniel Gunlycke, Brian L Chaloux
Orange crystals of a Sn14 cluster have been isolated in up to 22% yield from a reaction between Me3 SiCH2 SnCl3 , SnCl4 , and LiAlH4 . The structure determined by single crystal X-ray diffraction shows three unique Sn atoms in a 6:6:2 ratio, with all Sn atoms 4-coordinate, similar to the tetrahedral bonding in elemental gray Sn. The solid state 117 Sn MAS NMR spectrum shows the three types of distinct Sn atoms in the expected 3:3:1 intensity ratio with respective chemical shifts of 87.9, -66.6, and -607.1 ppm relative to Me4 Sn...
April 24, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29614256/interactions-of-staphyloxanthin-and-enterobactin-with-myeloperoxidase-and-reactive-chlorine-species
#3
Melanie S Coker, Louisa V Forbes, Matthew Plowman-Holmes, David R Murdoch, Christine C Winterbourn, Anthony J Kettle
When neutrophils engulf bacteria, myeloperoxidase converts hydrogen peroxide to hypochlorous acid, which is toxic to all micro-organisms. It has been suggested that some pathogens have virulence factors that target myeloperoxidase to dampen the oxidative reactions of neutrophils. These virulence factors include staphyloxanthin, the golden pigment of Staphylococcus aureus, and enterobactin - a siderophore released by gram-negative bacteria. We investigated the potential of staphyloxanthin and enterobactin to shield bacteria from hypochlorous acid and related chloramines...
March 31, 2018: Archives of Biochemistry and Biophysics
https://www.readbyqxmd.com/read/29610796/mechanism-of-ionic-liquid-based-acidic-aqueous-biphasic-system-formation
#4
Nicolas Schaeffer, Helena Passos, Matthieu Gras, Vijetha Mogilireddy, João P Leal, Germán Pérez-Sánchez, José R B Gomes, Isabelle Billard, Nicolas Papaiconomou, João A P Coutinho
Ionic-liquid-based acidic aqueous biphasic systems (IL-based AcABS) represent a promising alternative to the solvent extraction process for the recovery of critical metals, in which the substitution of the inorganic salt by an acid allows for a 'one-pot' approach to the leaching and separation of metals. However, a more fundamental understanding of AcABS formation remains wanting. In this work, the formation mechanisms of AcABS are elucidated through a comparison with traditional aqueous biphasic systems (ABS)...
April 3, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29164896/nuclear-magnetic-shielding-of-monoboranes-calculation-and-assessment-of-11-b-nmr-chemical-shifts-in-planar-bx-3-and-in-tetrahedral-bx-4-systems
#5
Jan Macháček, Michael Bühl, Jindřich Fanfrlík, Drahomír Hnyk
11 B NMR chemical shifts of tricoordinated BX3 and tetracoordinated BX4 - compounds (X = H, CH3 , F, Cl, Br, I, OH, SH, NH2 , and CH═CH2 ) were computed, and the shielding tensors were explored not only within the nonrelativistic GIAO approach but also by application of both relativistic ZORA computations including spin-orbit coupling as well as scalar nonrelativistic ZORA computations (BP86 level of density functional theory). The contributions of the spin-orbit coupling to the overall shieldings are decisive for X = Br and I in both series...
December 21, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29137153/halogen-bonding-involving-co-and-cs-with-carbon-as-the-electron-donor
#6
Janet E Del Bene, Ibon Alkorta, José Elguero
MP2/aug'-cc-pVTZ calculations have been carried out to investigate the halogen-bonded complexes formed when CO and CS act as electron-pair donors through C to ClF, ClNC, ClCl, ClOH, ClCN, ClCCH, and ClNH₂. CO forms only complexes stabilized by traditional halogen bonds, and all ClY molecules form traditional halogen-bonded complexes with SC, except ClF which forms only an ion-pair complex. Ion-pair complexes are also found on the SC:ClNC and SC:ClCl surfaces. SC:ClY complexes stabilized by traditional halogen bonds have greater binding energies than the corresponding OC:ClY complexes...
November 12, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28912146/cerenkov-activated-sticky-tag-for-in-vivo-fluorescence-imaging
#7
Sudeep Das, Katja Haedicke, Jan Grimm
A big challenge in the clinical use of Cerenkov luminescence (CL) imaging is its low signal intensity, which is several orders of magnitude below ambient light. Consequently, highly sensitive cameras, sufficient shielding from background light, and long acquisition times are required. To alleviate this problem, we hypothesized a strategy to convert the weak CL signal into a stronger fluorescence signal by using CL-activated formation of nitrenes from azides to locally fix a fluorescent probe in tissue by the formation of a covalent bond...
January 2018: Journal of Nuclear Medicine: Official Publication, Society of Nuclear Medicine
https://www.readbyqxmd.com/read/28650016/prediction-of-1-h-nmr-chemical-shifts-for-clusters-of-imidazolium-based-ionic-liquids
#8
Su Chen, Ekaterina I Izgorodina
Nuclear magnetic resonance (NMR) has been widely used to elucidate the bulk structure of ionic liquids. In this work, we calculated1 H NMR chemical shifts of 1-ethyl-3-methylimidazolium (C2 mim+ ) ionic liquids combined with various anions such as chloride (Cl), tetrafluoroborate (BF4 ), hexafluorophosphate (PF6 ), acetate (OAc), trifluoroacetate (TFA), and dicyanamide (DCA). The previously established level of theory, HF/6-311G+(3df,2p), was used for the accurate prediction of NMR chemical shifts both in gas phase and in solvents with varying dielectric constant such as CHCl3 and ethanol...
July 5, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28644553/structural-insights-into-the-inclusion-complexes-between-clomiphene-citrate-and-%C3%AE-cyclodextrin-the-mechanism-of-preferential-isomeric-selection
#9
Arti Maheshwari, Harish Saraswat, Santosh Kumar Upadhyay
A major challenge in pharmaceuticals for clinical applications is to alter the solubility, stability, and toxicity of drug molecules in living systems. Cyclodextrins (CDs) have the ability to form host-guest inclusion complexes with pharmaceuticals for further development of new drug formulations. The inclusion complex of clomiphene citrate (CL), a poorly water-soluble drug, with native β-cyclodextrin (β-CD) was characterized by a one and two-dimensional nuclear magnetic resonance (NMR) spectroscopic approach and also by molecular docking techniques...
August 2017: Chirality
https://www.readbyqxmd.com/read/28492643/the-influence-of-substituents-and-the-environment-on-the-nmr-shielding-constants-of-supramolecular-complexes-based-on-a-t-and-a-u-base-pairs
#10
Abril C Castro, Marcel Swart, Célia Fonseca Guerra
In the present study, we have theoretically analyzed supramolecular complexes based on the Watson-Crick A-T and A-U base pairs using dispersion-corrected density functional theory (DFT). Hydrogen atoms H8 and/or H6 in the natural adenine and thymine/uracil bases were replaced, respectively, by substituents X8, Y6 = NH- , NH2 , NH3 + (N series), O- , OH, OH2 + (O series), F, Cl or Br (halogen series). We examined the effect of the substituents on the hydrogen-bond lengths, strength and bonding mechanism, and the NMR shielding constants of the C2-adenine and C2-thymine/uracil atoms in the base pairs...
May 31, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28467047/electrophilic-halogenation-of-closo-1-2-c-2-b-8-h-10
#11
Mario Bakardjiev, Aleš Růžička, Zdeňka Růžičková, Josef Holub, Oleg L Tok, Bohumil Štíbr
Initial studies on electrophilic halogenation of the dicarbaborane closo-1,2-C2 B8 H10 (1) have been carried out to reveal that the substitution takes place at B7 and B10 vertexes, which are the most removed from the CH positions. The course of the halogenation is strongly dependent on the nature of the halogenation agent and reaction conditions. Individual reactions led to the isolation of the monosubstituted compounds 1,2-C2 B8 H9 -10-X (2) (where X = F, I) and 1,2-C2 B8 H9 -7-X (3) (where X = Cl, I). Disubstituted carboranes 1,2-C2 B8 H8 -7,10-X2 (4) (where X = Cl, Br, I) were obtained under more forcing conditions...
May 15, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28245022/computation-provides-chemical-insight-into-the-diverse-hydride-nmr-chemical-shifts-of-ru-nhc-4-l-h-0-species-nhc-n-heterocyclic-carbene-l-vacant-h-2-n-2-co-mecn-o-2-p-4-so-2-h-f-and-cl-and-their-ru-r-2-pch-2-ch-2-pr-2-2-l-h-congeners
#12
L Jonas L Häller, Elena Mas-Marzá, Mateusz K Cybulski, Rajashekharayya A Sanguramath, Stuart A Macgregor, Mary F Mahon, Christophe Raynaud, Christopher A Russell, Michael K Whittlesey
Relativistic density functional theory calculations, both with and without the effects of spin-orbit coupling, have been employed to model hydride NMR chemical shifts for a series of [Ru(NHC)4 (L)H]0/+ species (NHC = N-heterocyclic carbene; L = vacant, H2 , N2 , CO, MeCN, O2 , P4 , SO2 , H- , F- and Cl- ), as well as selected phosphine analogues [Ru(R2 PCH2 CH2 PR2 )2 (L)H]+ (R =i Pr, Cy; L = vacant, O2 ). Inclusion of spin-orbit coupling provides good agreement with the experimental data. For the NHC systems large variations in hydride chemical shift are shown to arise from the paramagnetic term, with high net shielding (L = vacant, Cl- , F- ) being reinforced by the contribution from spin-orbit coupling...
February 28, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28181618/-73-ge-119-sn-and-207-pb-general-cooperative-effects-of-single-atom-ligands-on-the-nmr-signals-observed-in-tetrahedral-mx-n-y-4-n-m-ge-sn-pb-1-%C3%A2-n-%C3%A2-4-x-y-cl-br-i-coordination-compounds-of-heavier-xiv-group-elements
#13
M Benedetti, F De Castro, F P Fanizzi
An inverse linear relationship between73 Ge,119 Sn and207 Pb NMR chemical shifts and the overall sum of ionic radii of coordinated halido ligands has been discovered in tetrahedral [MXn Y4-n ] (M = Ge, Sn, Pb; 1 ≤ n ≤ 4; X, Y = Cl, Br, I) coordination compounds. This finding is consistent with a previously reported correlation found in octahedral, pentacoordinate and square planar platinum complexes. The effect of the coordinated halido ligands acting on the metal as shielding conducting rings is therefore confirmed also by73 Ge,119 Sn and207 Pb NMR spectroscopy...
February 28, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28128302/augmented-laminography-a-correlative-3d-imaging-method-for-revealing-the-inner-structure-of-compressed-fossils
#14
Marcus Zuber, Michael Laaß, Elias Hamann, Sophie Kretschmer, Norbert Hauschke, Thomas van de Kamp, Tilo Baumbach, Thomas Koenig
Non-destructive imaging techniques can be extremely useful tools for the investigation and the assessment of palaeontological objects, as mechanical preparation of rare and valuable fossils is precluded in most cases. However, palaeontologists are often faced with the problem of choosing a method among a wide range of available techniques. In this case study, we employ x-ray computed tomography (CT) and computed laminography (CL) to study the first fossil xiphosuran from the Muschelkalk (Middle Triassic) of the Netherlands...
January 27, 2017: Scientific Reports
https://www.readbyqxmd.com/read/27993488/long-term-home-and-community-based-exercise-programs-improve-function-in-community-dwelling-older-people-with-cognitive-impairment-a-systematic-review
#15
Michelle Lewis, Casey L Peiris, Nora Shields
QUESTION: Do long-term (> 3 months) home or community-based exercise programs improve function, reduce falls and prevent hospital readmissions in older people with cognitive impairment? DESIGN: Systematic review and meta-analysis of randomised, controlled trials. Electronic databases (CINAHL, PubMed, Medline, Embase, AMED) were searched from the earliest date possible until March 2016. PARTICIPANTS: Older adults (≥ 65 years) with cognitive impairment living in the community...
January 2017: Journal of Physiotherapy
https://www.readbyqxmd.com/read/27871839/interactions-of-two-structurally-related-anionic-phospholipids-cardiolipin-and-phosphatidylglycerol-with-phospholipase-a2-langmuir-monolayer-studies
#16
Marcin Broniatowski, Monika Urbaś
Anionic phospholipids cardiolipins (CL) and phosphatidylglycerols (PG) dominate in the biomembranes of the majority of soil bacteria. CL to PG ratio differs between the species and is also dependent on the external conditions. CL/PG ratio is different in polluted than in unspoiled soils and it was hypothesized that it is connected with the activity of the membranelytic enzymes from the phospholipase A2 class (PLA2) as it was proved that persistent soil pollutants can activate PLA2. In our studies we applied the Langmuir monolayer technique and Brewster angle microscopy to elucidate the mechanism of the interactions of PLA2 with the model membranes formed by anionic phospholipids...
February 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/27412758/boron-as-an-electron-pair-donor-for-b%C3%A2-%C3%A2-%C3%A2-cl-halogen-bonds
#17
Ibon Alkorta, José Elguero, Janet E Del Bene
MP2/aug'-cc-pVTZ calculations were performed to investigate boron as an electron-pair donor in halogen-bonded complexes (CO)2 (HB):ClX and (N2 )2 (HB):ClX, for X=F, Cl, OH, NC, CN, CCH, CH3 , and H. Equilibrium halogen-bonded complexes with boron as the electron-pair donor are found on all of the potential surfaces, except for (CO)2 (HB):ClCH3 and (N2 )2 (HB):ClF. The majority of these complexes are stabilized by traditional halogen bonds, except for (CO)2 (HB):ClF, (CO)2 (HB):ClCl, (N2 )2 (HB):ClCl, and (N2 )2 (HB):ClOH, which are stabilized by chlorine-shared halogen bonds...
October 5, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/27295113/triptycene-based-chiral-and-meso-n-heterocyclic-carbene-ligands-and-metal-complexes
#18
Roman Savka, Marvin Bergmann, Yuki Kanai, Sabine Foro, Herbert Plenio
Based on 1-amino-4-hydroxy-triptycene, new saturated and unsaturated triptycene-NHC (N-heterocyclic carbene) ligands were synthesized from glyoxal-derived diimines. The respective carbenes were converted into metal complexes [(NHC)MX] (M=Cu, Ag, Au; X=Cl, Br) and [(NHC)MCl(cod)] (M=Rh, Ir; cod=1,5-cyclooctadiene) in good yields. The new azolium salts and metal complexes suffer from limited solubility in common organic solvents. Consequently, the introduction of solubilizing groups (such as 2-ethylhexyl or 1-hexyl by O-alkylation) is essential to render the complexes soluble...
July 4, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27074477/translating-bed-total-body-irradiation-lung-shielding-and-dose-optimization-using-asymmetric-mlc-apertures
#19
Shahbaz Ahmed, Derek Brown, Saad B S Ahmed, Muhammad B Kakakhel, Wazir Muhammad, Amjad Hussain
A revised translating bed total body irradiation (TBI) technique is developed for shielding organs at risk (lungs) to tolerance dose limits, and optimizing dose distribution in three dimensions (3D) using an asymmetrically-adjusted, dynamic multileaf collimator. We present a dosimetric comparison of this technique with a previously developed symmetric MLC-based TBI technique. An anthropomor-phic RANDO phantom is CT scanned with 3 mm slice thickness. Radiological depths (RD) are calculated on individual CT slices along the divergent ray lines...
March 8, 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/27031528/external-beam-radiation-for-choroidal-lymphoma-efficacy-and-complications
#20
Arman Mashayekhi, Murat Hasanreisoglu, Carol L Shields, Jerry A Shields
PURPOSE: To determine the efficacy and safety of external beam radiation for treatment of choroidal lymphoma (CL). DESIGN: Retrospective case series. PARTICIPANTS: Twenty-five eyes of 24 patients with CL treated with external beam radiation. METHOD: Review of medical records. MAIN OUTCOME MEASURES: Tumor control, visual acuity, and radiation complications. RESULTS: The mean age of the patients was 62 years (median, 65; range, 32-89 years)...
October 2016: Retina
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