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Observation of $Ξ_c(2930)^0$ and updated measurement of $B^-→K^-Λ^+_c\bar{Λ}^-_c$ at Belle
Here, we report the first observation of the $Ξ_c(2930)^0$ charmed-strange baryon with a significance greater than 5σ. The $Ξ_c(2930)^0$ is found in its decay to $K^-Λ^+_c$ in $B^-→K^-Λ^+_c\bar{Λ}^-_c$ decays. The measured mass and width are $[2928.9±3.0(stat.)^{+0.9}_{-12.0}(syst.)]$ MeV/ $c^2$ and $[19.5±8.4(stat.)^{+5.9}_{-7.9}(syst.)]$ MeV, respectively, and the product branching fraction is $\mathcal{B}(B^-→Ξ_c(2930)^0\bar{Λ}^-_c)\mathcal{B}(Ξ_c(2930)^0→K^-Λ^+_c)=[1.73±0.45(stat.)±0.21(syst.)]×10^{-4}$. We also measure $\mathcal{B}(B^-→K^-Λ^+_c\bar{Λ}^-_c)=[4.80±0.43(stat.)±0.60(syst.)]×10^{-4}$ with improved precision, and search for the charmonium-like state Y(4660) and its spin partner, Y η , in the $Λ^+_c\bar{Λ}^-_c$ invariant mass spectrum. No clear signals of the Y(4660) nor its spin partner are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of (772±11)×10 6 B B ¯ pairs collected at the Υ(4S) resonance by the Belle detector at the KEKB asymmetric energy electron–positron collider.
Synthesis and Isolation of the Titanium-Scandium Endohedral Fullerenes-Sc 2 TiC@ I h -C 80 , Sc 2 TiC@ D 5 h -C 80 and Sc 2 TiC 2 @ I h -C 80 : Metal Size Tuning of the Ti IV /Ti III Redox Potentials
The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc–Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH 4 and Ti/CH 4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc 4 C 2 @C 80 (the most abundant EMF from this synthesis), Sc 3 C 2 @C 80 , isomers of Sc 2 C 2 @C 82 , and the family Sc 2 C 2n (2 n=74, 76, 82, 86, 90, etc.), as well as Sc 3 CH@C 80 . The Sc–Ti/CH 4 system produces the mixed-metal Sc 2 TiC@C 2n (2 n=68, 78, 80) and Sc 2 TiC 2 @C 2n (2 n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc 2 TiC@Ih-C 80 , Sc 2 TiC@D 5h -C 80 , and Sc 2 TiC 2 @I h -C 80 , were characterized by NMR spectroscopy. The structure of Sc 2 TiC@I h -C 80
Evaporation of Cu, Sn, and S from Fe-C-Cu-Sn-S Liquid Alloys in the Temperature Range from 1513 K to 1873 K (1240 °C to 1600 °C)
Evaporation of Cu or Sn from liquid iron alloys containing C and S was experimentally investigated. The initial C concentration, [pct C] 0 , in the liquid alloy was varied from zero to C saturation, and the evaporation temperature was varied from 1513 K to 1773 K (1240 °C to 1500 °C). Along with the report by one of the present authors, the evaporation mechanism of Cu and Sn from liquid Fe-C-S alloy is proposed, after a modification from the previous mechanism. It was proposed that Cu and Sn evaporate as Cu(g) and Sn(g) and also evaporate as CuS(g) and SnS(g), which are more volatile species. Therefore, availability of S in the alloy affects the overall evaporation rate of Cu and Sn. At the same time, C in the alloy also forms volatile carbosulfides CS(g) and CS 2 (g), thereby competing with Cu and Sn. Moreover, C increases the activity coefficients of Cu, Sn, and S. This increases the thermodynamic driving force for the formation of CuS(g) and SnS(g). Therefore, increasing [pct C] partly accelerates the evaporation rate of Cu and Sn by increasing the activity coefficient but partly decelerates the evaporation rate by lowering the available S content. S partly accelerates the evaporation rate by increasing the available S for the sulfide gas species but partly decelerates the evaporation rate due to the surface poisoning effect. Increasing the reaction temperature increases the overall evaporation rate. All these facts were taken into account in order to develop an evaporation rate model. This model was extended from the present authors’ previous one by taking into account (1) CS(g), S(g), and CS{ 2 (g) (therefore, the following species were considered as dominant evaporating species: Cu(g), CuS(g), Sn(g), SnS(g), S(g), CS(g), and CS 2 (g)); (2) the effect of C and temperature on the activity coefficients of Cu, Sn, and S; (3) the effect of C and temperature on the density of the liquid alloy; and (4) the effect of temperature on the S adsorption coefficient. This revised evaporation model was used in order to explain the experimental data, and it showed good agreement. In particular, it was found that the temperature showed a significant effect on the evaporation rate, and the effect of temperature and C content on the activity coefficients of Cu, Sn, and S also significantly affected the evaporation rate. The chemical reaction rate constant of the individual evaporation reaction (k i } R ) and residual rate constant (k i r ) could be obtained as a function of temperature. The activation energy of each evaporation reaction was derived and discussed. The evaporation rate model can be applied in order to predict the content of Cu and Sn remaining in liquid iron under various conditions of temperature and [pct C].
Dynamics of the reaction of C{sub 2} with C{sub 6}H{sub 2}: An implication for the formation of interstellar C{sub 8}H
The reaction C{sub 2} + C{sub 6}H{sub 2} → C{sub 8}H + H was investigated for the first time. Reactant C{sub 2} (C{sub 6}H{sub 2}) was synthesized from 1% C{sub 3}F{sub 6}/He (5% C{sub 2}H{sub 2}/He) by pulsed high-voltage discharge. We measured the translational-energy distribution, the angular distribution, and the photoionization spectrum of product C{sub 8}H in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. This reaction released average translational energy of 8.5 kcal mol{sup −1} corresponding to a fraction of 0.37 in translation. C{sub 8}H was identified as octatetranyl based on the maximal translational-energy release 23 ± 2 kcal mol{sup −1} and the ionization threshold 8.9 ± 0.2 eV. Kinematic constraints can qualitatively account for the nearly isotropic angular distribution. The quantum-chemical calculations indicate that the exothermic reactions C{sub 2} (X {sup 1}Σ{sub g}{sup +}/a {sup 3}Π{sub u}) + HC{sub 6}H → C{sub 8}H + H can proceed without entrance and exit barriers, implying the importance in the cold interstellar medium. This work verifies that interstellar C{sub 8}H can be formed through the C{sub 2} + C{sub 6}H{sub 2} reaction.
Quantum-chemical calculations of the metallofullerene yields in the X@C{sub 74}, L@C{sub 74}, and Z@C{sub 82} series
The contribution reports computations for Al@C{sub 82}, Sc@C{sub 82}, Y@C{sub 82} and La@C{sub 82} based on encapsulation into the IPR (isolated pentagon rule) C{sub 2ν} C{sub 82} cage and also on Mg@C{sub 74}, Ca@C{sub 74}, Sr@C{sub 74} and Ba@C{sub 74} based on encapsulation into the only C{sub 74} IPR cage as well as for three selected lanthanoids La@C{sub 74}, Yb@C{sub 74}, and Lu@C{sub 74}. Their structural and energetic characteristics are used for evaluations of the relative production yields, using the encapsulation Gibbs-energy and saturated metal pressures. It is shown that the results can be well related to the ionization potentials of the free metal atoms.
Measuring Long-Range 13 C– 13 C Correlations on a Surface under Natural Abundance Using Dynamic Nuclear Polarization-Enhanced Solid-State Nuclear Magnetic Resonance [Measuring Long Range 13 C– 13 C Correlations on Surface under Natural Abundance Using DNP-enhanced Solid-state NMR]
Here, we report that spatial (<1 nm) proximity between different molecules in solid bulk materials and, for the first time, different moieties on the surface of a catalyst, can be established without isotope enrichment by means of homonuclear CHHC solid-state nuclear magnetic resonance experiment. This 13 C– 13 C correlation measurement, which hitherto was not possible for natural-abundance solids, was enabled by the use of dynamic nuclear polarization. Importantly, it allows the study of long-range correlations in a variety of materials with high resolution.
1,2-Propanediol as a Surrogate Molecule of Glycerol for Mechanistic Studies of Selective Hydrodeoxygenation Reactions over Mo 2 C and Cu/Mo 2 C Surfaces
The upgrading of glycerol, a byproduct from biodiesel production, is important for developing more sustainable biomass conversion technologies. Nonetheless, the low vapor pressure and structural complexity of glycerol limit mechanistic studies of gas-phase reactions on model surfaces and powder catalysts. In this work, we demonstrate the feasibility of using 1,2-propanediol (PDO) as a surrogate compound for the mechanistic study of glycerol over Mo 2 C and Cu/Mo 2 C surfaces. Here, the results show that glycerol and 1,2-PDO undergo similar reaction pathways on both the Mo and Cu sites, suggesting that 1,2-PDO could be used as a higher vapor pressure surrogate to glycerol for gas-phase mechanistic studies.
Precise measurement of the branching fractions of J / ψ → Λ ¯ π + Σ − + c . c . and J / ψ → Λ ¯ π − Σ + + c . c .
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Measurements of ψ ( 3686 ) → K − Λ Ξ ¯ + + c . c . and ψ ( 3686 ) → γ K − Λ Ξ ¯ + + c . c .
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Observation of e + e − → γ χ c 1 and search for e + e − → γ χ c 0 , γ χ c 2 , and γ η c at s near 10.6 GeV at Belle
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Triketiminate bis(borohydride) complexes of rare-earth metals [(2,6-Me{sub 2}C{sub 6}H{sub 3}N=CMe){sub 2}C(2,6-Me{sub 2}C{sub 6}H{sub 3}N=CBu{sup t})]Ln(BH{sub 4}){sub 2}(THF){sub 2} (Ln = Y, Nd): synthesis, structure, and catalytic activity in polymerization of rac-lactide, ε-caprolactone, and isoprene
A new triketimine (2,6-Me{sub 2}C{sub 6}H{sub 3}N=CMe){sub 2}CH(2,6-Me{sub 2}C{sub 6}H{sub 3}N=CBu{sup t}) (1) was synthesized by the reaction of imidoyl chloride 2,6-Me{sub 2}C{sub 6}H{sub 3}N=CClBu{sup t} with lithium diketiminate (2,6-Me{sub 2}C{sub 6}H{sub 3}N=CMe){sub 2}CHLi. In the crystalline state, compound 1 exists in the diimineenamine form; in solution, in the triimine form. The metalation of triketimine 1 with n-butyllithium in THF at 0 °C produced lithium triketiminate [(2,6-Me{sub 2}C{sub 6}H{sub 3}N=CMe){sub 2}C(2,6-Me{sub 2}C{sub 6}H{sub 3}N=CBu{sup t})]Li(THF){sub 2} (2). The metathesis reactions of Ln(BH{sub 4}){sub 3}(THF){sub 3} (Ln = Y, Nd) with compound 2 (1: 1 molar ratio, THF) gave the neutral triketiminate bis(borohydride) complexes [(2,6-Me{sub 2}C{sub 6}H{sub 3}N=CMe){sub 2}C(2,6-Me{sub 2}C{sub 6}H{sub 3}N=CBu{sup t})]Ln(BH{sub 4}){sub 2}(THF){sub 2} (Ln = Y (3), Nd (4)). As opposed to the complexes with neutral triketimine, the monoanionic triketiminate ligand is coordinated to Li and Y or Nd cations in a bidentate fashion. Complexes 3 and 4 catalyze the polymerization of rac-lactide and ε-caprolactone; in combination with [Ph{sub 3}C][B(C{sub 6}F{sub 5}){sub 4}] and AlBu{sub 3}{sup i} (1 : 1 : 10 molar ratio), these compounds exhibit catalytic activity in the polymerization of isoprene.
Search for η c ( 2 S ) → π + π − η c and η c ( 2 S ) → π + π − K S 0 K ± π ∓ decays
Based on ( 27.12 ± 0.14 ) × 10 8 ψ ( 2 S ) events collected by the BESIII detector, we search for the decay η c ( 2 S ) → π + π − η c via ψ ( 2 S ) → γ η c ( 2 S ) . No significant signal is observed, and the upper limit on the product branching fraction B ( ψ ( 2 S ) → γ η c ( 2 S ) ) × B ( η c ( 2 S ) → π + π − η c ) is determined to be 2.21 × 10 − 5 at the 90% confidence level. In addition, the η c ( 2 S ) → π + π − K S 0 K ± π ∓ decay is studied via ψ ( 2 S ) → γ η c ( 2 S ) and is observed with a statistical significance of 10 σ for the first time. The branching fraction of η c ( 2 S ) → π + π − K S 0 K ± π ∓ is determined to be ( 1.33 ± 0.11 ± 0.40 ± 0.95 ) × 10 − 2 , where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the quoted B ( ψ ( 2 S ) → γ η c ( 2 S ) ) . Published by the American Physical Society 2024
Quantification of C=C and C=O Surface Carbons in Detonation Nanodiamond by NMR
The ability of solid-state 13C NMR to detect and quantify small amounts of sp2-hybridized carbon on the surface of ~5 nm diameter nanodiamond particles is demonstrated. The C=C carbon fraction is only 1.1 ± 0.4% in pristine purified detonation nanodiamond, while a full single-layer graphitic or “bucky diamond” shell would contain ca. 25% of all C in a 5 nm diameter particle. Instead of large aromatic patches repeatedly proposed in the recent literature, sp3-hybridized CH and COH carbons cover most of the nanodiamond particle surface, accounting for ~5% each. C=O and COO groups also seen in X-ray absorption near-edge structure spectroscopy (XANES) but not detected in previous NMR studies make up ca. 1.5% of all C. They are removed by heat treatment at 800 °C, which increases the aromatic fraction. 13C{1H} NMR demonstrates that the various sp2-hybridized carbons are mostly not protonated, but cross-polarization shows that they are separated from 1H by only a few bond lengths, which proves that they are near the protonated surface. Together, the observed C–H, C–OH, C=O, and C=C groups account for 12–14% of all C, which matches the surface fraction expected for bulk-terminated 5 nm diameter diamond particles.
Accurate measurements of {sup 13}C-{sup 13}C distances in uniformly {sup 13}C-labeled proteins using multi-dimensional four-oscillating field solid-state NMR spectroscopy
Application of sets of {sup 13}C-{sup 13}C internuclear distance restraints constitutes a typical key element in determining the structure of peptides and proteins by magic-angle-spinning solid-state NMR spectroscopy. Accurate measurements of the structurally highly important {sup 13}C-{sup 13}C distances in uniformly {sup 13}C-labeled peptides and proteins, however, pose a big challenge due to the problem of dipolar truncation. Here, we present novel two-dimensional (2D) solid-state NMR experiments capable of extracting distances between carbonyl ({sup 13}C′) and aliphatic ({sup 13}C{sub aliphatic}) spins with high accuracy. The method is based on an improved version of the four-oscillating field (FOLD) technique [L. A. Straasø, M. Bjerring, N. Khaneja, and N. C. Nielsen, J. Chem. Phys. 130, 225103 (2009)] which circumvents the problem of dipolar truncation, thereby offering a base for accurate extraction of internuclear distances in many-spin systems. The ability to extract reliable accurate distances is demonstrated using one- and two-dimensional variants of the FOLD experiment on uniformly {sup 13}C,{sup 15}N-labeled-L-isoleucine. In a more challenging biological application, FOLD 2D experiments are used to determine a large number of {sup 13}C′-{sup 13}C{sub aliphatic} distances in amyloid fibrils formed by the SNNFGAILSS fibrillating core of the human islet amyloid polypeptide with uniform {sup 13}C,{sup 15}N-labeling on the FGAIL fragment.
Study of Azimuthal Correlations in the Target Fragmentation Region in p, d, He, C+C, Ta and C+Ne, Cu Collisions at a Momentum of 4.2, 4.5 and 10 AGeV/c
Azimuthal correlations between the same type of particles (protons or pions) in the target fragmentation region was studied in d, He, C + C, Ta (4.2 AGeV/c), C + Ne, Cu (4.5AGeV/c) and p + C, Ta (10 GeV/c) interactions. The data were obtained from the SKM-200-GIBS streamer chamber and from Propane Bubble Chamber (PBL-500) systems utilized at JINR. Study of multiparticle azimuthal correlations offers unique information about space-time evolution of the interactions. Azimuthal correlations were investigated by using correlation function C($\Delta\phi$)=dN/d($\Delta\phi$), where $\Delta\phi$ represents the angle between the sums of transverse momenta vectors for particles emitted in the forward and backward hemispheres. For protons a "back-to back" ("negative") azimuthal correlations were observed in the above mentioned interactions. The absolute values of the correlation coefficient $|\xi|$ -- the slope parameter of C($\Delta\phi$), strongly depend on the mass number of the target ($A_T$) nuclei in the nucleon-nucleus and nucleus-nucleus collisions. Namely, $|\xi|$ -- decreases with increase of $A_T$ in p+C and p+Ta collisions, while $|\xi|$ decreases from d+C up to C+Ne and then almost does not change with increase of $A_P$, $A_T$ in (d+He)Ta, C+Cu and C+Ta collisions. For pions a "back-to-back" correlations were obtained for a light targets (C, Ne), and a "side-by-side" ("positive") correlations for a heavy targets (Cu, Ta). The $|\xi|$ insignificantly changes with increase of the momenta per nucleon and almost does not change with increase of $A_P$ and $A_T$. Models, used for description of the data -- the Ultra relativistic Quantum Molecular Dynamic (UrQMD) and Quark-Gluon String Model (QGSM), satisfactorily describe the obtained experimental results.
Measurement of the Cross Sections of Ξ c 0 and Ξ c + Baryons and of the Branching-Fraction Ratio BR ( Ξ c 0 → Ξ − e + ν e ) / BR ( Ξ c 0 → Ξ − π + ) in p p Collisions at s = 13 TeV
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