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| 11. |
- Adcox, K, et al.
(författare)
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PHENIX detector overview
- 2003
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 499:2-3, s. 469-479
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Tidskriftsartikel (refereegranskat)abstract
- The PHENIX detector is designed to perform a broad study of A-A, p-A, and p-p collisions to investigate nuclear matter under extreme conditions. A wide variety of probes, sensitive to all timescales, are used to study systematic variations with species and energy as well as to measure the spin structure of the nucleon. Designing for the needs of the heavy-ion and polarized-proton programs has produced a detector with unparalleled capabilities. PHENIX measures electron and muon pairs, photons, and hadrons with excellent energy and momentum resolution. The detector consists of a large number of subsystems that are discussed in other papers in this volume. The overall design parameters of the detector are presented. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 12. |
- Aartsen, M. G., et al.
(författare)
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Multiwavelength follow-up of a rare IceCube neutrino multiplet
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 607
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Tidskriftsartikel (refereegranskat)abstract
- On February 17, 2016, the IceCube real-time neutrino search identified, for the first time, three muon neutrino candidates arriving within 100 s of one another, consistent with coming from the same point in the sky. Such a triplet is expected once every 13.7 years as a random coincidence of background events. However, considering the lifetime of the follow-up program the probability of detecting at least one triplet from atmospheric background is 32%. Follow-up observatories were notified in order to search for an electromagnetic counterpart. Observations were obtained by Swift's X-ray telescope, by ASAS-SN, LCO and MASTER at optical wavelengths, and by VERITAS in the very-high-energy gamma-ray regime. Moreover, the Swift BAT serendipitously observed the location 100 s after the first neutrino was detected, and data from the Fermi LAT and HAWC observatory were analyzed. We present details of the neutrino triplet and the follow-up observations. No likely electromagnetic counterpart was detected, and we discuss the implications of these constraints on candidate neutrino sources such as gamma-ray bursts, core-collapse supernovae and active galactic nucleus flares. This study illustrates the potential of and challenges for future follow-up campaigns.
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| 13. |
- Reifarth, R., et al.
(författare)
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Nuclear astrophysics with radioactive ions at FAIR
- 2016
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 665:1
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Konferensbidrag (refereegranskat)abstract
- The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
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| 14. |
- Scandale, Walter, et al.
(författare)
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Apparatus to study crystal channeling and volume reflection phenomena at the SPS H8 beamline
- 2008
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 79:2
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Tidskriftsartikel (refereegranskat)abstract
- A high performance apparatus has been designed and built by the H8-RD22 collaboration for the study of channeling and volume reflection phenomena in the interaction of 400 GeVc protons with bent silicon crystals, during the 2006 data taking in the external beamline H8 of the CERN SPS. High-quality silicon short crystals were bent by either anticlastic or quasimosaic effects. Alignment with the highly parallel (8 μrad divergence) proton beam was guaranteed through a submicroradian goniometric system equipped with both rotational and translational stages. Particle tracking was possible by a series of silicon microstrip detectors with high-resolution and a parallel plate gas chamber, triggered by various scintillating detectors located along the beamline. Experimental observation of volume reflection with 400 GeVc protons proved true with a deflection angle of (10.4±0.5) μrad with respect to the unperturbed beam, with a silicon crystal whose (111) planes were parallel to the beam. © 2008 American Institute of Physics.
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| 16. |
- Axfors, Cathrine, et al.
(författare)
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Association between convalescent plasma treatment and mortality in COVID-19 : a collaborative systematic review and meta-analysis of randomized clinical trials
- 2021
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Ingår i: BMC Infectious Diseases. - : BioMed Central (BMC). - 1471-2334. ; 21:1
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Forskningsöversikt (refereegranskat)abstract
- Background: Convalescent plasma has been widely used to treat COVID-19 and is under investigation in numerous randomized clinical trials, but results are publicly available only for a small number of trials. The objective of this study was to assess the benefits of convalescent plasma treatment compared to placebo or no treatment and all-cause mortality in patients with COVID-19, using data from all available randomized clinical trials, including unpublished and ongoing trials (Open Science Framework, ). Methods: In this collaborative systematic review and meta-analysis, clinical trial registries (ClinicalTrials.gov, WHO International Clinical Trials Registry Platform), the Cochrane COVID-19 register, the LOVE database, and PubMed were searched until April 8, 2021. Investigators of trials registered by March 1, 2021, without published results were contacted via email. Eligible were ongoing, discontinued and completed randomized clinical trials that compared convalescent plasma with placebo or no treatment in COVID-19 patients, regardless of setting or treatment schedule. Aggregated mortality data were extracted from publications or provided by investigators of unpublished trials and combined using the Hartung-Knapp-Sidik-Jonkman random effects model. We investigated the contribution of unpublished trials to the overall evidence. Results: A total of 16,477 patients were included in 33 trials (20 unpublished with 3190 patients, 13 published with 13,287 patients). 32 trials enrolled only hospitalized patients (including 3 with only intensive care unit patients). Risk of bias was low for 29/33 trials. Of 8495 patients who received convalescent plasma, 1997 died (23%), and of 7982 control patients, 1952 died (24%). The combined risk ratio for all-cause mortality was 0.97 (95% confidence interval: 0.92; 1.02) with between-study heterogeneity not beyond chance (I-2 = 0%). The RECOVERY trial had 69.8% and the unpublished evidence 25.3% of the weight in the meta-analysis. Conclusions: Convalescent plasma treatment of patients with COVID-19 did not reduce all-cause mortality. These results provide strong evidence that convalescent plasma treatment for patients with COVID-19 should not be used outside of randomized trials. Evidence synthesis from collaborations among trial investigators can inform both evidence generation and evidence application in patient care.
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| 17. |
- Ivanov, Alexander V., et al.
(författare)
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Crystalline cadmium dialkyl phosphorodithioate complexes : synthesis and structural organization as probed by multinuclear C-13, P-31, and Cd-113 CP/MAS NMR and single-crystal X-ray diffraction
- 2007
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Ingår i: Russian Journal of Inorganic Chemistry. - 0036-0236 .- 1531-8613. ; 52:10, s. 1595-1602
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Tidskriftsartikel (refereegranskat)abstract
- The cadmium O,O'-dethyl (I) and O,O'-di-sec-butyl phosphorodithioate (II) complexes have been synthesized and characterized in detail by(13)C, P-31, and Cd-113 CP/MAS NMR. X-ray crystallography shows that complex II has a binuclear molecular structure [Cd-2{S2P(O-s-C4H9)(2)}(4)]. For P-31 and Cd-113 NMR signals, the chemical shift anisotropy delta(aniso) and the asymmetry parameter eta have been calculated. The P-31 NMR signals are assigned to the terminal and bridging ligands in the complexes.
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| 18. |
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| 19. |
- Ivanov, M.A., et al.
(författare)
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Tetraphenylantimony(V) O,O″-dialkyl dithiophosphates [Sb(C 6H5)4{S2P(OR)2}] (R = s-C4H9, c-C6H11) : synthesis, structures, and 13C and 31P CP/MAS NMR spectra
- 2008
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Ingår i: Russian journal of coordination chemistry. - 1070-3284 .- 1608-3318. ; 34:7, s. 527-535
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Tidskriftsartikel (refereegranskat)abstract
- Tetraphenylantimony(V) O,O′-di-sec-butyl dithiophosphate (I) and tetraphenylantimony(V) O,O′-dicyclohexyl dithiophosphate (II) [Sb(C 6H5)4{S2P(OR)2}] (R = sec-C4H9 or cyclo-C6H11) were obtained. Their structures and spectroscopic properties were studied by X-ray diffraction analysis and 13C and 31P CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in complexes I and II were found to be coordinated in S-monodentate and S,S′-bidentate fashions, respectively (MAS NMR data). According to X-ray diffraction data, the coordination polyhedron of antimony in molecular structure I is a trigonal bipyramid with unusual monodentate coordination of the Dtph group in the axial position.
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| 20. |
- Scandale, Walter, et al.
(författare)
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Deflection of 400GeV/c proton beam with bent silicon crystals at the CERN Super Proton Synchrotron
- 2008
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 11:6
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a detailed study of the deflection phenomena of a 400GeV/c proton beam impinging on a new generation of bent silicon crystals; the tests have been performed at the CERN Super Proton Synchrotron H8 beam line. Channeling and volume reflection angles are measured with an extremely precise goniometer and with high resolution silicon microstrip detectors. Volume reflection has been observed and measured for the first time at this energy, with a single-pass efficiency as large as 98%, in good agreement with the simulation results. This efficiency makes volume reflection a possible candidate for collimation with bent crystals at the CERN Large Hadron Collider. © 2008 The American Physical Society.
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| 21. |
- Sharutin, V. V., et al.
(författare)
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Tetraphenyl- and tetratolylantimony complexes with N,N-dialkyldithiocarbamate ligands : synthesis, X-ray diffraction analysis, and 13C and 15N CP/MAS NMR studies
- 2006
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Ingår i: Russian journal of coordination chemistry. - 1070-3284 .- 1608-3318. ; 32:3:6, s. 87-396
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Tidskriftsartikel (refereegranskat)abstract
- Crystalline tetraphenylantimony and tetratolylantimony complexes with N,N-dialkyldithiocarbamate ligands [Sb(C6H5)4(S2CNR2)] (R = CH3, C2H5, and C3H7 and R2 = (CH2)6) were synthesized by ligand exchange reactions and studied by 13C and 15N CP/MAS NMR spectroscopy. X-ray diffraction analysis revealed that the complex [Sb(n-CH3-C6H4)4{S2CN(C3H7)2}] exists as the single molecular form, while [Sb(C6H5)4{S2CN(CH2)6}] exists as two molecular conformers. The 13C and 15N signals were assigned to the positions of the atoms in the isomeric structures [Sb(C6H5)4{S2CN(CH2)6}] in terms of different degrees of double bonding in the formally single =N-C(S)S-bond.
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| 22. |
- Ivanov, Alexander V., et al.
(författare)
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A comparative study of the structural organization of nickel(II) and copper(II) complexes with dialkyl-substituted and cyclic dithiocarbamate ligands by X-ray single-crystal diffraction, EPR, and CP/MAS C-13 and N-15 NMR
- 2002
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Ingår i: Russian Journal of Inorganic Chemistry. - 0036-0236 .- 1531-8613. ; 47:3, s. 410-422
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Tidskriftsartikel (refereegranskat)abstract
- X-ray single-crystal diffraction, EPR, and CP/MAS C-13 and N-15 NMR were used for studying the structures and spectral properties of nickel(II) and copper(II) dithiocarbamate complexes [M(S2CNR2)(2)] (R = CH3, C2H5, C3H7, i-C3H7 or R-2 = (CH2)(5), (CH2)(6), (CH2)(4)O). The [CUS4] chromophores in the lattice of nickel(II) complexes have, predominantly, a square-planar structure. The chromophore geometry is somewhat distorted only in bis(morpholinedithiocarbamato)copper(II). Differences in the N-15 NMR isotropic chemical shifts of dialkyldithiocarbamate ligands were interpreted in terms of a unified conceptual approach based on the concept of joint manifestation of the mesomeric effect of dithiocarbamate groups and the inductive effect of alkyl substituents. Experimental NMR (C-13, N-15) signals were assigned to the structural positions of atoms in allowed molecular structures. Refined structural data on [Ni{S2CN(C3H7)(2)}(2)] point to the occurrence of two types of structurally nonequivalent complex molecules; the [Ni(S2CN(CH2)6)2] complex is characterized by the intramolecular nonequivalence of dithiocarbamate ligands.
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| 23. |
- Ivanov, Alexander V., et al.
(författare)
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Binding of Au3+ from solutions by nickel(II) and cadmium diisopropyl dithiophosphates: MAS P-31 NMR, structure and thermal behavior of the polynuclear complex [Au-2{S2P(O-iso-C3H7)(2)}(2)] (n)
- 2012
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Ingår i: Russian journal of coordination chemistry. - 1070-3284 .- 1608-3318. ; 38:6, s. 430-439
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Tidskriftsartikel (refereegranskat)abstract
- The paper deals with reactions of freshly precipitated diisopropyl dithiophosphate (Dtph) complexes of nickel(II), [Ni{S2P(O-iso-C3H7)(2)}(2)] and cadmium, [Cd-2{S2P(O-iso-C3H7)(2)}(4)], with the [AuCl4](-) in 2M HCl, resulting in gold transition from the solution to the precipitate as polymeric gold(I) diisopropyl dithiophosphate. The reduction of gold(III) to gold(I) noted in both cases is due to oxidation of the relevant part of the Dtph group to bis(O,O'-di-(iso)-propoxythiophosphoryl) disulfide, (iso-C3H7O)(2)P(S)S-S(S)P(O-iso-C3H7)(2). The polynuclear gold(I) complex [Au-2{S2P(O-iso-C3H7)(2)}(2)] (n) (I) was isolated on a preparative scale from the chemisorption system and studied by MAS P-31 NMR and X-ray diffraction. The key structural unit of I is the non-centrosymmetric binuclear molecule [Au-2{S2P(O-iso-C3H7)(2)}(2)] in which the gold atoms are connected by two bridging Dtph groups. The structure contains two types of non-equivalent binuclear molecules related as conformational isomers. Owing to the relatively weak Au-Au contacts, the neighboring binuclear [Au-2{S2P(O-iso-C3H7)(2)}(2)] molecules are involved in an infinite polymeric chain with conformer alternation along the chain. To elucidate the conditions for the recovery of bound gold(I), the precipitates formed in the sorption systems were studied by simultaneous thermal analysis under argon. As the final product, thermolysis gives reduced metallic gold. The ability of dithiophosphate complexes to bind gold from a solution is much lower than that of dithiocarbamate complexes, which is due to oxidation of some Dtph groups to disulfide.
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| 24. |
- Ivanov, Alexander V., et al.
(författare)
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Chemisorption Synthesis of the Ion-Polymeric Heteronuclear Gold(III)-Bismuth(III) Complex ([Au{S2CN(C3H7)2}2]3[Bi2Cl9])n Based on [Bi2{S2CN(C3H7)2}6]: 13C MAS NMR, Supramolecular Structure, and Thermal Behavior
- 2018
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Ingår i: Russian journal of coordination chemistry. - : Springer. - 1070-3284 .- 1608-3318. ; 44:8, s. 518-531
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Tidskriftsartikel (refereegranskat)abstract
- Chemisorption synthesis on the basis of the binuclear compound [Bi2{S2CN(C3H7)2}6] (I) and preparative isolation of the ion-polymeric heteronuclear gold(III)-bismuth(III) complex ([Au{S2CN(C3H7)2}2]3[Bi2Cl9])n (II) are carried out. Compounds I and II are characterized in comparison by IR spectroscopy and 13C CP-MAS NMR. According to the X-ray diffraction analysis data (CIF file CCDC no. 1407705), the cationic moiety of compound II exhibits an unusually complicated supramolecular structure including six isomeric noncentrosymmetric complex cations [Au{S2CN(C3H7)2}2]+ (hereinafter A-F) and two binuclear anions [Bi2Cl9]3- as conformers. The isomeric gold(III) cations perform various structural functions. Owing to pair secondary interactions Au···S, cations B, C, E, and F form centrosymmetric ([E···E], [F···F]) and noncentrosymmetric ([B···C]) binuclear aggregates [Au2{S2CN(C3H7)2}4]2+, whereas cations A and D are not involved in dimerization. The strongest secondary Au···S bonds are formed between the binuclear and mononuclear cations, resulting in the formation of supramolecular cation-cationic polymer chains of two types: (⋅⋅⋅A⋅⋅⋅[B⋅⋅⋅C]⋅⋅⋅A⋅⋅⋅[B⋅⋅⋅C]⋅⋅⋅)n and (D⋅⋅⋅[E⋅⋅⋅E]⋅⋅⋅D⋅⋅⋅[F⋅⋅⋅F]⋅⋅⋅])n. In both chains, the gold atoms of the binuclear cations are characterized by a distorted octahedral coordination [S6], whereas in the mononuclear cations the gold atoms retain the square environment [S4]. The cation-anionic interactions are provided by secondary bonds Cl⋅⋅⋅S involving the terminal chlorine atoms of isomeric [Bi2Cl9]3- and the sulfur atoms of the binuclear cations [Au2{S2CN(C3H7)2}4]2+. The character of the thermal behavior of compounds I and II is studied by simultaneous thermal analysis with the identification of intermediate and final products of the thermal transformations. The thermolysis of compound I at 193-320°C is accompanied by the formation of Bi2S3 with an impurity of reduced metallic bismuth particles. The final products of the thermal transformations of compound II are reduced elemental gold and Bi2O3, and the thermal transformation intermediates are BiCl3 and Bi2S3.
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| 25. |
- Ivanov, M.A., et al.
(författare)
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Synthesis, structure, and 13C and 31P CP/MAS NMR of the tetraphenylantimony(V) di-iso-propyl phosphorodithioate complex [Sb(C6H5)4{S2P(O-iso-C3H7)2}] and its solvated form [Sb(C6H5)4{S2P(O-iso-C3H7)2}] · 1/2C6H6 : an example of the monodentate coordination of dithio ligands
- 2009
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Ingår i: Russian Journal of Inorganic Chemistry. - 0036-0236 .- 1531-8613. ; 54:5, s. 708-716
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Tidskriftsartikel (refereegranskat)abstract
- The crystalline tetraphenylantimony(V) O,O′-di-iso-propyl phosphorodithioate complex [Sb(C6H5)4{S2P(O-i-C3H7)2}](I) and its solvated form [Sb(C6H5)4{S2P(O-i-C3H7)2}] · 1/2C6H6(II) were synthesized. Solid compounds I and II were studied by MAS NMR (13C, 31P). The 31P NMR chemical shift anisotropy 31P δaniso = (δ zz - δiso) and asymmetry parameter η = (δ yy - δ xx )/(δ zz - δiso) were calculated using χ 2 plots constructed on the basis of the 31P MAS NMR data. The O,O′-di-iso-propyl phosphorodithioate ligands in both complexes are characterized by predominantly the axially symmetric 31P chemical shift tensor (for the case δ zz < δ xx ≈ δ yy ) with close values of anisotropy parameters (δaniso and η), which reflects their identical S-monodentate structural function. X-ray crystallography showed that II has a trigonal-bipyramidal molecular structure with the uncommon monodentate coordination of the Dtph ligands through an S atom in an axial position of the trigonal bipyramid and the benzene molecule in the outer sphere.
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| 26. |
- Korablev, Oleg I., et al.
(författare)
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Infrared Spectrometer for ExoMars: A Mast-Mounted Instrument for the Rover
- 2017
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Ingår i: Astrobiology. - : Mary Ann Liebert. - 1531-1074 .- 1557-8070. ; 17:6-7, s. 542-564
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Tidskriftsartikel (refereegranskat)abstract
- ISEM (Infrared Spectrometer for ExoMars) is a pencil-beam infrared spectrometer that will measure reflected solar radiation in the near infrared range for context assessment of the surface mineralogy in the vicinity of the ExoMars rover. The instrument will be accommodated on the mast of the rover and will be operated together with the panoramic camera (PanCam), high-resolution camera (HRC). ISEM will study the mineralogical and petrographic composition of the martian surface in the vicinity of the rover, and in combination with the other remote sensing instruments, it will aid in the selection of potential targets for close-up investigations and drilling sites. Of particular scientific interest are water-bearing minerals, such as phyllosilicates, sulfates, carbonates, and minerals indicative of astrobiological potential, such as borates, nitrates, and ammonium-bearing minerals. The instrument has an ∼1° field of view and covers the spectral range between 1.15 and 3.30 μm with a spectral resolution varying from 3.3 nm at 1.15 μm to 28 nm at 3.30 μm. The ISEM optical head is mounted on the mast, and its electronics box is located inside the rover's body. The spectrometer uses an acousto-optic tunable filter and a Peltier-cooled InAs detector. The mass of ISEM is 1.74 kg, including the electronics and harness. The science objectives of the experiment, the instrument design, and operational scenarios are described.
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| 27. |
- Plakhova, Tatiana V., et al.
(författare)
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Towards the surface hydroxyl species in CeO2 nanoparticles
- 2019
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Ingår i: Nanoscale. - : ROYAL SOC CHEMISTRY. - 2040-3364 .- 2040-3372. ; 11:39, s. 18142-18149
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the complex chemistry of functional nanomaterials is of fundamental importance. Controlled synthesis and characterization at the atomic level is essential to gain deeper insight into the unique chemical reactivity exhibited by many nanomaterials. Cerium oxide nanoparticles have many industrial and commercial applications, resulting from very strong catalytic, pro- and anti-oxidant activity. However, the identity of the active species and the chemical mechanisms imparted by nanoceria remain elusive, impeding the further development of new applications. Here, we explore the behavior of cerium oxide nanoparticles of different sizes at different temperatures and trace the electronic structure changes by state-of-the-art soft and hard X-ray experiments combined with computational methods. We confirm the absence of the Ce(III) oxidation state at the surface of CeO2 nanoparticles, even for particles as small as 2 nm. Synchrotron X-ray absorption experiments at Ce L-3 and M-5 edges, combined with X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and small angle X-ray scattering (SAXS) and theoretical calculations demonstrate that in addition to the nanoceria charge stability, the formation of hydroxyl groups at the surface profoundly affects the chemical performance of these nanomaterials.
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| 28. |
- Rodina, Tatyana A., et al.
(författare)
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Crystalline O,O’-di-sec-butyl and O,O’-diethyl dithiophosphate platinum(II) complexes : Synthesis, 13C and 31P CP/MAS NMR, single crystal X-ray diffraction studies and thermal behaviour
- 2011
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Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 30:13, s. 2210-2217
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Tidskriftsartikel (refereegranskat)abstract
- Crystalline bis(O,O’-di-sec-butyldithiophosphato)platinum(II) was prepared and studied by means of 31P, 13C CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the platinum(II) compound is comprised of one centrosymmetric mononuclear molecule [Pt{S2P(O-sec-C4H9)2}2], in which the dithiophosphate groups display structural equivalence in both 31P NMR and XRD data. A pair of the dithiophosphate ligands exhibit the same S,S’-bidentate chelating structural function and form two planar four-membered chelate rings, [PtS2P], in this molecule. The planar configuration of the [PtS4] chromophore in structure 1 is governed by the dsp2-hybrid state of platinum(II). The structural states of the dithiophosphate groups in two different samples of complex 1 (one crystallised from ethanol and the other one precipitated from an aqueous solution) are all characterised by almost rhombic 31P chemical shift tensors. The observed essential dispersion of the 31P NMR chemical shift is caused by a coexistence of six optical isomers of molecule 1. The thermal behaviour of this compound was studied by means of simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour shows that the mass of 1 is lost in three steps, involving successive thermal decompositions of the organic and inorganic parts of this compound with platinum(II) dithio-meta-phosphate and reduced metallic platinum as the intermediate and the final products, respectively.
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| 29. |
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| 30. |
- Farnocchia, Davide, et al.
(författare)
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International Asteroid Warning Network Timing Campaign: 2019 XS
- 2022
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Ingår i: The Planetary Science Journal. - : Institute of Physics Publishing (IOPP). - 2632-3338. ; 3:7
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Tidskriftsartikel (refereegranskat)abstract
- As part of the International Asteroid Warning Network's observational exercises, we conducted a campaign to observe near-Earth asteroid 2019 XS around its close approach to Earth on 2021 November 9. The goal of the campaign was to characterize errors in the observation times reported to the Minor Planet Center, which become an increasingly important consideration as astrometric accuracy improves and more fast-moving asteroids are observed. As part of the exercise, a total of 957 astrometric observations of 2019 XS during the encounter were reported and subsequently were analyzed to obtain the corresponding residuals. While the timing errors are typically smaller than 1 s, the reported times appear to be negatively biased, i.e., they are generally earlier than they should be. We also compared the observer-provided position uncertainty with the cross-track residuals, which are independent of timing errors. A large fraction of the estimated uncertainties appear to be optimistic, especially when <0 2. We compiled individual reports for each observer to help identify and remove the root cause of any possible timing error and improve the uncertainty quantification process. We suggest possible sources of timing errors and describe a simple procedure to derive reliable, conservative position uncertainties.
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| 31. |
- Ivanov, Alexander, et al.
(författare)
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Structural organization of mercury(II) and copper(II) dithiocarbamates from EPR and 13C and 15N MAS NMR spectra and X-ray diffraction analysis
- 2008
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Ingår i: Russian journal of coordination chemistry. - : Springer Science and Business Media LLC. - 1070-3284 .- 1608-3318. ; 34:1, s. 59-69
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Tidskriftsartikel (refereegranskat)abstract
- The structures and spectroscopic properties of mononuclear and binuclear mercury(II) and copper(II) complexes with four dithiocarbamate ligands R 2NC(S)S- (R = CH3, C2H5, or iso-C3H7; R2 = (CH2)6) were studied by solid-state 13C and 15N CP/MAS NMR and EPR spectroscopy. Mercury(II) N,N-cyclohexamethylenedithiocarbamate [Hg 2{S2CN(CH2)6}4] was obtained and characterized in detail by X-ray diffraction analysis at 299 K. The binuclear molecule of the complex is centrosymmetric; the central tricyclic fragment [Hg2S4C2] is in the chair conformation. In the 13C and 15N NMR spectra, the signals were assigned to the dithiocarbamate ligands with different structural functions: bidentate chelating and combined (both chelating and bridging) ones. The differences between the isotropic 15N chemical shifts for the dialkyldithiocarbamate ligands were interpreted in terms of combination of the mesomeric effect of the =NC(S)S-groups and the inductive effect of the alkyl substituents. According to the EPR data, copper(II) in magnetically diluted systems is mainly found in heterobinuclear molecules [CuHg(S2CNR 2)4] and the geometry of the chromophores [CuS 5] approximates to a tetragonal pyramid.
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| 32. |
- Ivanov, Alexander V., et al.
(författare)
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A comparative study of the structural organization of zinc complexes with dialkyl-substituted and cyclic dithiocarbamate ligands : synthesis, single-crystal X-ray diffraction, and CP/MAS C-13 and N-15 NMR
- 2003
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Ingår i: Russian Journal of Inorganic Chemistry. - 0036-0236 .- 1531-8613. ; 48:1, s. 45-54
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Tidskriftsartikel (refereegranskat)abstract
- The structures and spectral properties of eight zinc(II) dithiocarbamate complexes [Zn-2(S2CNR2)(4)] (R = CH3, C2H5, C3H7, C3H7, C4H9; or R-2 = (CH2)(5), (CH2)(6), (CH2)(4)O) have been studied by single-crystal X-ray diffraction and CP/MAS C-13 and N-15 NMR. The experimental C-13 and N-15 NMR signals have been assigned to the positions of the corresponding atoms in the ligands with different structural functions (terminal or bridging). Differences in the N-15 NMR isotropic chemical shifts of dialkyldithiocarbamate ligands have been interpreted based on the concept of joint manifestation of the mesometic effect of dithiocarbamate groups and the inductive effect of alkyl substituents. The zinc dibutyl-, pentamethylene-, and morpholinedithiocarbamate complexes have been prepared and comprehensively characterized. The binuclear complex [Zn-2{S2CN(C4H9)(2)}(4)] appears to be the second example of a noncentrosymmetiic molecule of zinc dithiocarbamate. Another structural feature of the dimer is the fact that the eight-membered [Zn2S4C2] metallacycle is stabilized in the boat rather than in the chair conformation.
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| 33. |
- Ivanov, Alexander V., et al.
(författare)
-
Conformational isomerism of the binuclear N,N-pentamethylenedithiocarbamate cadmium(II) complex, [Cd2{S2CN(CH2)5}4] on multinuclear (15N, 113Cd) CP/MAS NMR and single-crystal X-ray diffraction data
- 2006
-
Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693 .- 1873-3255. ; 359:12, s. 3855-3864
-
Tidskriftsartikel (refereegranskat)abstract
- Crystalline N,N-cyclo-pentamethylenedithiocarbamate (PmDtc) cadmium(II) complex was prepared and studied by means of 15N, 113Cd CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the cadmium(II) compound comprises two centrosymmetric isomeric binuclear molecules [Cd2{S2CN(CH2)5}4], which display structural inequivalence in both 15N and 113Cd NMR and XRD data. There are pairs of the dithiocarbamate ligands exhibiting different structural functions in both isomeric molecules. Each of the terminal ligands is bidentately coordinated to the cadmium atom and forms a planar four-membered chelate ring [CdS2C]; whereas pairs of the tridentate bridging ligands combine two neighbouring cadmium atoms forming an extended eight-membered tricyclic moieties [Cd2S4C2], whose geometry can be approximated by a ‘chair' conformation. The structural states of cadmium atoms were characterised by almost axially symmetric 113Cd chemical shift tensors. All experimental 15N resonance lines were assigned to the nitrogen structural sites in both isomeric binuclear molecules.
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| 34. |
- Ivanov, Alexander V., et al.
(författare)
-
Polymeric thallium(I) O,O′-diisopropyl dithiophosphate [Tl{S2P(O-iso-C3H7)2}]n : synthesis, structure, and 13C and 31P CP/MAS
- 2009
-
Ingår i: Russian journal of coordination chemistry. - 1070-3284 .- 1608-3318. ; 35:11, s. 857-863
-
Tidskriftsartikel (refereegranskat)abstract
- The crystalline polymeric thallium(I) O,O′-diisopropyl dithiophosphate [Tl{S2P(O-iso-C3H7)2}] n (I) was obtained and examined by solid-state 13C and 31P CP/MAS NMR spectroscopy. Diagrams of the χ2 statistic were constructed from the complete 31P MAS NMR spectra and used to calculate the 31P chemical shift anisotropy (δaniso = (δ zz - δiso)) and the asymmetry parameter (η = (δ yy - δ xx )/(δ zz - δiso)). The 31P chemical shift tensor has a nearly axial symmetry (η = 0.22, δ zz < δ yy ≈ δ xx ). The MAS NMR spectral patterns correspond to the negative sign of δaniso (δ zz < δ yy < δ xx ), which indicates bridging or chelating-bridging coordination of the dithiophosphate ligands (Dtph). X-ray diffraction analysis revealed a polymeric structure of compound I. The polymer chain consists of alternating mononuclear [Tl{S2P(O-iso-C3H7)2}] molecules with opposite spatial orientations. The Dtph ligands are coordinated in a mixed, chelating-μ3-bridging fashion. The shape of the 31P NMR signal was interpreted in terms of the 31P-203,205Tl coupling pattern proposed from crystallographic data.
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| 35. |
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| 36. |
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| 37. |
- Ivanov, Alexander V., et al.
(författare)
-
Structural organization of nickel(II), zinc(II), and copper(II) complexes with diisobutyldithiocarbamate : EPR, 13C and 15N CP/MAS NMR, and X-ray diffraction studies
- 2005
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Ingår i: Russian journal of coordination chemistry. - : Springer Science and Business Media LLC. - 1070-3284 .- 1608-3318. ; 31:10, s. 695-707
-
Tidskriftsartikel (refereegranskat)abstract
- The structures and spectroscopic properties of nickel(II), zinc(II), and copper(II) complexes with dibutyl- and diisobutyldithiocarbamate were studied by EPR and 13C and 15N CP/MAS NMR spectroscopy and X-ray diffraction analysis. According to the EPR data, copper(II) forms mononuclear [63/65Cu{S2CNR2}2] and heterobinuclear complexes [63/65CuZn{S2CNR2}4] under magnetic dilution conditions. The isomeric forms of nickel(II) and zinc(II) diisobutyldithiocarbamates were detected by 13C and 15N NMR spectroscopy. The crystalline zinc(II) diisobutyldithiocarbamate was found to have a unique structural organization with alternating mononuclear [Zn{S2CN(i-C4H9)2}2] and binuclear molecular forms [Zn2{ S2CN(i-C4H9)2}4] in the 1 : 1 ratio.
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| 38. |
- Ivanov, Alexander V., et al.
(författare)
-
Synthesis, structural and multinuclear natural abundance (C-13, P-31, Pt-195) CP/MAS NMR studies of crystalline O,O '-dialkyldithiophosphate platinum(II) complexes
- 2008
-
Ingår i: Russian journal of coordination chemistry. - 1070-3284 .- 1608-3318. ; 34:8, s. 584-593
-
Tidskriftsartikel (refereegranskat)abstract
- Platinum(II) O,O'-dicyclohexyl dithiophosphate [Pt{S2P(O-cyclo-C6H11)(2)}(2)] (I) and platinum(II) O,O'-diisopropyl dithiophosphate [Pt{S2P(O-iso-C3H7)(2)}(2)] (II) complexes were obtained and studied by solidstate C-13, P-31, and Pt-195 CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in molecular structure I were found to be coordinated by platinum in S,S'-bidentate fashion to form the planar chromophore [PtS4] (single-crystal X-ray diffraction data). For complex II, a new alpha-form (alpha-II) was obtained and identified by P-31 MAS NMR spectroscopy. The P-31 chemical shift anisotropy delta(aniso) and the asymmetry parameter eta of the P-31 chemical shift tensor were calculated from the whole MAS spectra.
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| 39. |
- Ivanov, Maxim A., et al.
(författare)
-
Preparation and structural organisation of heteroleptic tetraphenylantimony(V) complexes comprising unidentately and bidentately coordinated O,O'-dialkyldithiophosphate groups : multinuclear (C-13 P-31) CP/MAS NMR and single-crystal X-ray diffraction studies
- 2007
-
Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693 .- 1873-3255. ; 360:9, s. 2897-2904
-
Tidskriftsartikel (refereegranskat)abstract
- O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate (Dtph) tetraphenylantimony(V) complexes of the general formula [Sb(C6H5)4{S2P(OR)2}] (R = C3H7, i-C4H9) were prepared and studied by means of 13C, 31P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. Distorted octahedral and trigonal bipyramidal molecular structures have been established for prepared complexes. These unexpected structural distinctions between chemically related compounds are defined by the principally different coordination modes of O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate ligands in their molecular structures (i.e., S,S′-bidentate chelating and S-unidentately coordinated, respectively). To characterise quantitatively phosphorus sites in both species of dithiophosphate ligands, 31P chemical shift anisotropy parameters (δaniso and η) were calculated from spinning sideband manifolds in MAS NMR spectra. The 31P chemical shift tensors for the bidentate chelating and unidentately coordinated dithiophosphate ligands display a profoundly rhombic and nearly axially symmetric characters, respectively.
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| 40. |
- Kattge, Jens, et al.
(författare)
-
TRY plant trait database - enhanced coverage and open access
- 2020
-
Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
-
Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 41. |
- Korneeva, E.V., et al.
(författare)
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Crystalline nickel(II) di-i-amyl dithiophosphate, [Ni{S2P(O-i-C5H11)2}2] : Preparation, structure, heteronuclear (13C, 31P) CP/MAS NMR spectra, and thermal behavior
- 2017
-
Ingår i: Russian journal of coordination chemistry. - : Springer. - 1070-3284 .- 1608-3318. ; 43:4, s. 223-231
-
Tidskriftsartikel (refereegranskat)abstract
- The crystalline nickel(II) di-i-amyl) dithiophosphate (Dtph), [Ni{S2P(O-i-C5H11)2}2] (I) was isolated on a preparative scale and characterized by 13C, 31P MAS NMR, and X-ray diffraction (CIF file CCDC no. 1469369). The χ2-statistic diagrams were constructed from full 31P CP/MAS NMR spectra for calculating the 31P chemical shift anisotropy: δaniso = δzz–δiso and the asymmetry parameter η = (δyy–δxx)/(δzz–δiso). The key structural unit of I is the centrosymmetric [Ni{S2P(O-i-C5H11)2}2] molecule in which the nickel atom coordinates two Dtph ligands in the isobidentate fashion. In molecule I, each carbon, oxygen, and sulfur atom is statistically disordered over two sites with equal occupancies. However, the disorder does not affect nickel and phosphorus. These results were interpreted as the presence in I of two [Ni{S2P(O-i-C5H11)2}2] molecules rotated through 21.0(1)° (the angle between the [NiS4] chromophore planes) relative to each other around the bisecting P–Ni–P axis passing through both four-membered [NiS2P] rings. The two molecules occupy crystal lattice sites with equal probabilities. The thermal behavior of I was studied by simultaneous thermal analysis under argon. The course of the thermal destruction of the complex was established, nickel pyrophosphate (Ni2P2O7) was identified as the final product of thermal transformations.
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| 42. |
- Larsson, Anna-Carin, et al.
(författare)
-
Synthesis of four different antimony(III) O,O’-dialkyldithiophosphates : characterization by 31P CP/MAS NMR, single crystal X-ray diffraction, and adsorption at a stibnite surface (Sb2S3)
- 2012
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 368:1, s. 488-495
-
Tidskriftsartikel (refereegranskat)abstract
- Four different dialkyldithiophosphate (DTP) ions, (RO)2PSS– (R = C3H7, iso-C3H7, iso-C4H9, cyclo-C6H11) have been adsorbed on the surface of synthetically prepared stibnite, Sb2S3, and studied by means of 31P CP/MAS NMR. Corresponding individual [Sb{(S2P(OR)2}3] complexes have also been synthesized and used for comparison with the surface adsorbed DTP species. The results show that a low concentration of collector at the surface leads to a chemisorbed monolayer of DTP on the mineral surface. At high concentration of DTP, a surface precipitate of Sb(DTP)3 is formed. 31P CP/MAS NMR and chemical shift anisotropy data indicate that the S–P–S bite angle of the chemisorbed DTP groups on the surface is larger than in the corresponding precipitated complexes and the coordination of the ligands differ. Using single-crystal X-ray diffraction technique, the molecular structure of a solvated form of crystalline O,O’-di-cyclo-hexyldithiophosphate antimony(III) complex has been resolved. In this novel molecular structure, the central antimony atom S,S’-anisobidentately coordinates three structurally non-equivalent DTP groups and, therefore, the geometry of the [SbS6] chromophore can be approximated by a distorted octahedron. Besides that, useful correlations between 31P CSA parameters and structural data on this complex were also established.
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| 43. |
- Menushenkov, A. P., et al.
(författare)
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Direct evidence of real-space pairing in BaBiO3
- 2024
-
Ingår i: Physical Review Research. - : American Physical Society. - 2643-1564. ; 6:2
-
Tidskriftsartikel (refereegranskat)abstract
- The parent compound BaBiO3 of bismuthate high-temperature superconductors (HTSCs) BaBi(Pb)O3 and Ba(K)BiO3 with perovskitelike structure exhibits unusual electronic and structural properties, which can be satisfactorily explained if we assume that all charge carriers are in the paired state. However, the prior experiments and the first-principle calculations only indirectly indicate the existence of paired charge carriers in BaBiO3. In this work, we report the direct evidence of initially paired electrons and holes in the upper antibonding Bi 6s-O 2p sigma* orbital of the neighboring octahedral complexes in the ground state of BaBiO3 using the time-resolved x-ray absorption spectroscopy (XAS) to monitor the electron dynamics after the femtosecond resonant 633 nm laser excitation. We observe strong changes in the oxygen K-edge XAS preedge region, defined by the Bi 6s-O 2p sigma* orbitals. We interpret them as a fast (<= 0.3 ps) breaking of charge carrier pairs and slower (0.3-0.8 ps) lattice rearrangement from the distorted monoclinic structure into the new metastable state with a cubic lattice, which persists at least up to 60 ps after the excitation. Analysis of the intermediate state at the fast excitation shows that the bond disproportionation and monoclinic distortion of BaBiO3 structure are energetically favorable due to the charge carrier pairing. Thus the compound BaBiO3 forms a new quantum state that we define as a local pair density wave. Taking into account a large number of similarities between bismuthate and cuprate high-temperature superconductors, we believe that our work will give a new impetus to understanding the nature of superconductivity in perovskite HTSCs.
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| 44. |
- Rodina, Tatyana A., et al.
(författare)
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Fixation modes of gold(III) from solutions using cadmium(II) dithiocarbamates : Preparation, supramolecular structure and thermal behaviour of polynuclear and heteropolynuclear gold(III) complexes: bis(N,N-dialkyldithiocarbamato-S,S’)gold(III) polychlorometallates, [Au(S2CNR2)2]nX (n =1: X = [AuCl4]–; n = 2: X = [CdCl4]2–, [Cd2Cl6]2–)
- 2012
-
Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 40:1, s. 53-64
-
Tidskriftsartikel (refereegranskat)abstract
- Four novel heteropolynuclear and polynuclear complexes of the general formulae [Au(S2CNR2)2]2X (X = [CdCl4]2-, R = CH3 (1); X = [Cd2Cl6]2-, R = C3H7 (2)) and [Au(S2CNR2)2][AuCl4] (R = iso-C3H7 (3); R = iso-C4H9 (4)) were prepared using heterogeneous reactions between appropriate freshly precipitated binuclear cadmium(II) dialkyl dithiocarbamates and AuCl3 in 2 M hydrochloric acid. The isolated complexes were studied by 13C CP/MAS NMR spectroscopy, single-crystal X-ray diffraction and simultaneous thermal analysis (STA) under an argon atmosphere. In all molecular structures (1–4), one of the gold atoms coordinates two dialkyl dithiocarbamate ligands in the S,S’-bidentate mode, forming a square-planar coordination polygon [AuS4], while the other gold atom (in 3 and 4) has four neighbouring chlorine atoms [AuCl4]. At the supramolecular level, compounds 1 and 2 comprise binuclear cations, [Au2{S2CN(CH3)2}4]2+ and polynuclear chains, ([Au{S2CN(C3H7)2}2]+)n in a combination with [CdCl4]2- and [Cd2Cl6]2- anions, respectively. Unexpected structural distinctions at the supramolecular level were discovered for the chemically related compounds 3 and 4. In these ionic complexes, there are either cationic trinuclear formations, {[Au{S2CN(iso-C3H7)2}2]2[AuCl4]}+, or polynuclear chains, ([Au{S2CN(iso-C4H9)2}2]+)n, both combined with [AuCl4]– anions, in the structural basis of compounds 3 and 4, respectively.
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| 45. |
- Rodina, T.A., et al.
(författare)
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Synthesis, structure, and 13C and 31P CP/MAS NMR of crystalline modifications of the polynuclear thallium(I) O,O′-dicyclohexyl phosphorodithioate complex [Tl{S2P(O-cyclo-C6H11)2}]n
- 2009
-
Ingår i: Russian Journal of Inorganic Chemistry. - 0036-0236 .- 1531-8613. ; 54:11, s. 1779-1788
-
Tidskriftsartikel (refereegranskat)abstract
- Two crystalline modifications (Ia and Ib) of the polynuclear thallium (I) O,O′-dicyclohexyl phosphorodithioate complex [Tl{S2P(O-cyclo-C6H11)2}] n have been synthesized and characterized by CP/MAS NMR (13C, 31P). From full 31P CP/MAS NMR spectra, the χ2 plots were constructed to calculate the 31P chemical shift anisotropy 31P - δaniso = (δzz - δiso) and asymmetry parameters η = (δ yy - δ xx )/(δ zz - δiso). The data obtained for the O,O′-dicyclohexyl phosphorodithioate (Dtph) groups (in both modifications) are evidence that the 31P chemical shift tensors are intermediate between rhombic and axially symmetric. However, whereas the rhombic component dominates for Ia, the tensor for Ib is close to axially symmetric (for δ zz < δ yy ≈ δ xx ). The same pattern of the MAS spectra corresponding to negative δaniso (δ zz < δ yy < δ xx ) points to a bridging or terminal/bridging coordination mode of the Dtph groups. X-ray crystallography shows that complex Ib has a polynuclear structure (of the chain polymer type). The chains are composed of alternating structurally nonequivalent noncentrosymmetric binuclear molecules [Tl2{S2P(O-cyclo-C6H11)2}2]. All Dtph ligands have the terminal/μ3-bridging coordination mode.
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| 46. |
- Zaeva, Anna S., et al.
(författare)
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Dialkyldithiocarbamate platinum(II) complexes of [Pt(S2CNR2)2] (R = iso-C3H7, iso-C4H9) : Preparation, 13C CP-MAS NMR, molecular structure, supramolecular self-assembly and thermal behaviour
- 2020
-
Ingår i: Polyhedron. - : Elsevier. - 0277-5387 .- 1873-3719. ; 175
-
Tidskriftsartikel (refereegranskat)abstract
- Two new dialkyldithiocarbamato platinum(II) complexes of [Pt(S2CNR)2], R = iso-C3H7 (1) and iso-C4H9 (2), have been prepared and characterised using 13C CP-MAS NMR. The crystal and molecular structures of the isolated compounds were established by single-crystal X-ray diffraction. The unit cell of 1 contains four centrosymmetric discrete molecules of [Pt{S2CN(iso-C3H7)2}2], of which the pairs are structurally inequivalent to each other (hereafter denoted as molecules 1a and 1b). At the supramolecular level, due to numerous intermolecular C–H···S hydrogen bonds, the 1a molecules form linear polymeric ribbons, whose interaction with the 1b molecules results in a two-dimensional polymeric network. In the structure of 2, the construction of supramolecular zigzag chains by non-centrosymmetric molecules of [Pt{S2CN(iso-C4H9)2}2] is determined by intermolecular C–H···Pt anagostic interactions. The thermal behaviour of crystalline compounds 1 and 2 was studied by simultaneous thermal analysis (STA), a combination of the TG and DSC techniques, under an argon atmosphere. In both cases, platinum(II) sulphide (PtS) was identified as the main end-product upon thermal decomposition of the complexes at 600 °C.
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| 47. |
- Afanasiev, Sergey V., et al.
(författare)
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Experimental apparatus to study crystal channeling in an external SPS beamline
- 2007
-
Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6634
-
Tidskriftsartikel (refereegranskat)abstract
- For the new generation of high intensity hadronic machines as, for instance, LHC, halo collimation is a necessary issue for the accelerator to operate at the highest possible luminosity and to prevent the damage of superconductor magnets.1 We propose an experiment aimed to systematic study of the channeling phenomenology and of the newly observed "volume reflection" effect. This experiment will be performed for an external SPS beamline and will make use of a primary proton beam with 400 GeV/c momentum and very small (∼ 3 μrad) divergence. The advantage of a proposed experiment is precise tracking of particles that interacted with a crystal, so that to determine the single-pass efficiency for all the processes involved. For this purpose, a telescope equipped with high-resolution silicon microstrip detectors will be used. New generation silicon crystals and an extra-precise goniometer are mandatory issues. Main goal of the experiment is to get the precise information on channeling of relativistic particles and, ultimately, on the feasibility of such technique for halo collimation at LHC. In this contribution we review the status of the setting-up of experimental apparatus and its future development in sight of the planned run in September 2006.
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| 48. |
- Bredyuk, O.A., et al.
(författare)
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Three-Dimensional Polymeric Thallium(I) Morpholinedithiocarbamate [Tl2{S2CN(CH2)4O}2]n and Its Capability of Binding Gold(III) from Solutions : Chemisorption Synthesis of a Heteronuclear Gold(III)–Thallium(III) Complex of the Ionic Type, ([Au{S2CN(CH2)4O}2][TlCl4])n, the Role of Secondary Interactions Tl…O, Tl…S, and Au…S in the Supramolecular Self-Organization, 13C MAS NMR, and Thermal Behavior
- 2017
-
Ingår i: Russian journal of coordination chemistry. - : Maik Nauka Publishing. - 1070-3284 .- 1608-3318. ; 43:10, s. 638-651
-
Tidskriftsartikel (refereegranskat)abstract
- Crystalline polymeric thallium(I) morpholinedithiocarbamate [Tl2{S2CN(CH2)4O}2]n (I) and the heteronuclear ion–polymeric gold(III)–thalium(III) complex ([Au{S2CN(CH2)4O}2][TlCl4])n (II) are preparatively isolated and characterized by X-ray diffraction analysis and 13C MAS NMR spectroscopy. According to the X-ray diffraction data, the main structural units of compounds I and II (CIF files CCDC 1548079 and 1548080) are presented by the binuclear centrosymmetric molecule [Tl2{S2CN(CH2)4O}2], noncentrosymmetric complex cation [Au{S2CN(CH2)4O{2]+, and isomeric complex anions [TlCl4]–. The formation of the three-dimensional polymeric structure (coordination number of Tl is 7), which is not characteristic of thallium(I) dithiocarbamates, is a consequence of the participation of the secondary Tl…O and Tl…S bonds of two types in the supramolecular self-organization of compound I. Nonequivalent secondary interactions of the first type join the binuclear molecules [Tl2{S2CN(CH2)4O}2] into polymer layers, which, in turn, form the three-dimensional polymeric framework due to the secondary bonds Tl…S. The revealed ability of freshly precipitated compound I to the chemisorption of gold(III) from solutions (2 M HCl) makes it possible to obtain heteronuclear supramolecular complex II as an individual form of binding. In the structure of the latter, the pairs of stronger secondary Au…S bonds join the gold(III) cations into dimers [Au2{S2CN(CH2)4O}4]2+ of the angular structure, the structural ordering of which is achieved in the cationcationic polymeric chain ([Au2{S2CN(CH2)4O}4]2+)n of the helical type involving the pairs of less strong Au…S bonds between the adjacent binuclear units. The distorted tetrahedral anions [TlCl4]– are localized between the polymeric chains. The study of the thermal behavior of compounds I and II by simultaneous thermal analysis makes it possible to establish the character of thermal transformations of the substances and to identify Tl2S (I), TlCl, and elemental gold (II) as thermolysis products
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| 49. |
- Farnocchia, Davide, et al.
(författare)
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The Second International Asteroid Warning Network Timing Campaign: 2005 LW3
- 2023
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Ingår i: The Planetary Science Journal. - : Institute of Physics (IOP). - 2632-3338. ; 4:11
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Tidskriftsartikel (refereegranskat)abstract
- The Earth close approach of near-Earth asteroid 2005 LW3 on 2022 November 23 represented a good opportunity for a second observing campaign to test the timing accuracy of astrometric observation. With 82 participating stations, the International Asteroid Warning Network collected 1046 observations of 2005 LW3 around the time of the close approach. Compared to the previous timing campaign targeting 2019 XS, some individual observers were able to significantly improve the accuracy of their reported observation times. In particular, U.S. surveys achieved good timing performance. However, no broad, systematic improvement was achieved compared to the previous campaign, with an overall negative bias persisting among the different observers. The calibration of observing times and the mitigation of timing errors should be important future considerations for observers and orbit computers, respectively.
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| 50. |
- Ivanov, Alexander, et al.
(författare)
-
A fixation mode of gold from solutions using heterogeneous reaction of cadmium dicyclohexyl dithiophosphate with H[AuCl4]. Structural and (13C, 31P) CP/MAS NMR studies and thermal behaviour of crystalline polymeric gold(I) dicyclohexyl dithiophosphate and bis(dicyclohexylthiophosphoryl) disulphide
- 2013
-
Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 1034, s. 152-161
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Tidskriftsartikel (refereegranskat)abstract
- Two novel compounds: polynuclear catena-poly[bis(3-O,O’-di-cyclo-hexyldithiophosphato-S,S,S’)digold(I)] (Au–Au) (1) and crystalline bis(O,O’-di-cyclo-hexylthiophosphoryl)disulphide, (cyclo-C6H11O)2P(S)S–S(S)P(O-cyclo-C6H11) (2) were prepared using heterogeneous reaction between freshly precipitated binuclear cadmium(II) dithiophosphate (Dtph), [Cd2{S2P(O-cyclo-C6H11}4] and H[AuCl4] in 2 M hydrochloric acid. The isolated compounds 1 and 2 (the fixation mode of gold from the solution and the oxidised form of Dtph groups, respectively) have been studied by means of single-crystal X-ray diffraction, 13C and 31P cross-polarisation / magic-angle-spinning (CP/MAS) NMR spectroscopy and simultaneous thermal analysis (STA). Centrosymmetric binuclear molecule of 1, [Au2{S2P(O-cyclo-C6H11)2}2] comprises a pair of -bridging di-cyclo-hexyl Dtph ligands, linking two neighbouring gold atoms, and displays additional intramolecular aurophilic bond Au···Au. At the supramolecular level of structural self-organisation of complex 1, infinite polymeric zigzag chains arise due to pairs of the secondary bonds Au···S between neighbouring binuclear molecules. Centrosymmetric molecule of 2 displays two O,O-di-cyclo-hexythiophosphoryl fragments, which are connected by the chemical bond S(1)–S(1)a, and a planar zigzag array [S=P–S–S–P=S] passing through the central part of the molecule. To characterise additionally the Dtph groups in both compounds 1 and 2, chemical shift anisotropy (CSA) parameters (aniso and) were calculated from spinning sideband manifolds in experimental 31P MAS NMR spectra. The thermal behaviour of complex 1 was studied using simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour displays stepwise mass loss, comprising thermal decompositions of the organic and inorganic parts of 1 with gold(I) dithio-meta-phosphate and reduced metallic gold as the intermediate and the final products, respectively.
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