The N = 16 Spherical Shell Closure in 24O

The unbound excited states of the most neutron-rich dripline oxygen isotope, ²⁴O, have been investigated by using the ²⁴O(p,p′)²⁴O^* reaction at the beam energy of 62 MeV/nucleon in inverse kinematics. The first and second unbound excited states of ²⁴O have been observed at ${E_{\rm x}= 4.63_{-0.14}^{+0.30}}$  MeV and ${E_{\rm x}= 5.13_{-0.24}^{+0.19}}$  MeV (preliminary) along with the evidence for another higher lying state at around 7.3 MeV. The quadrupole deformation parameter ${\beta_{2^+}}$ was deduced to be ${0.15_{-0.03}^{+0.08}}$ (preliminary) for the first time. The systematics of the ${\beta_{2^+}}$ and the ${E_{\rm x}(2_1^+)}$ in the Z = 8 isotopes shows the N = 16 spherical shell closure in ²⁴O.     

Doping induced evolution of Fermi surface in low carrier superconductor Tl-doped PbTe

We have performed high-resolution angle-resolved photoemission spectroscopy on Tl-doped PbTe. We observed a distinct energy shift of the valence band and core levels upon Tl doping, together with the evolution of a small hole pocket around the X[over] point in the Brillouin zone, while no clear evidence for the localized states near the Fermi level is observed. These experimental results suggest that direct hole doping into the valence band and resultant emergence of a small Fermi surface are responsible for the metallic conductivity in Tl-doped PbTe.     

Conformal equations that are not Virasoro or Weyl invariant

Letters in Mathematical Physics - While the argument by Zamolodchikov and Polchinski suggests global conformal invariance implies Virasoro invariance in two-dimensional unitary conformal field...     

New dopant precursors for n-type and p-type GaN

Tetraethylsilane (TeESi) and bis(ethylcyclopentadienyl)Mg (ECp₂Mg) were employed as Si and Mg dopant precursors for MOVPE growth of n-type and p-type GaN films, respectively. In Si doping, the electron concentration was observed to increase with the increase of the TeESi flow rate. The temperature dependence of the Hall mobility showed good agreement with n-type GaN films grown using different dopant precursors (SiH₄, GeH₄, Si₂H₆). The donor activation energy was estimated to be 27 meV, which is almost the same as the literature values. In Mg doping, we also found that the Mg concentration increases as the ECp₂Mg flow rate increases. All of Mg-doped samples in this study showed p-type conduction after annealing. The acceptor activation energy was estimated to be 170 meV, which was close to the reported values.     

Aerobic photo-decarboxylation of α-hydroxy carboxylic acid derivatives under visible light irradiation in the presence of catalytic iodine

A catalytic amount of iodine enables us to carry out aerobic photo-decarboxylation of α-hydroxy carboxylic acid derivatives to the corresponding carboxylic acids or ketones selectively in high yields under irradiation of vis. This new oxidation is interesting in keeping with the notion of Green Chemistry due to the non-use of heavy metals and halogenated solvents, waste reduction, and the use of molecular oxygen.     

Vibronic interaction in metalloporphyrin pi-anion radicals

The vibronic (vibrational-electronic) interactions in the pi-anion radicals of the metalloporphyrins (M=Cr, Mn, Fe, Co, Ni, Cu, and Zn), which show delocalized D4h structures in the neutral states, are discussed using B3LYP density-functional-theory calculations. The B1g and B2g modes of vibration can remove the degenerate 2Eg state of the pi-anion radicals in the D4h symmetric structures to lead to rectangular and diamond D2h distortions, respectively. Calculated vibronic coupling constants demonstrate that the B1g modes of vibration better couple with the degenerate electronic state, leading to the rectangular D2h distortion. In particular, the B1g modes of nu10 and nu11, which have dominant contributions from Calpha-Cm and Cbeta-Cbeta stretching, give large vibronic coupling constants in the pi-anion radicals. The vibronic coupling constant can be viewed as the Jahn-Teller distortion force, and therefore these C-C stretching B1g modes will play a central role in the Jahn-Teller effect of the pi-anion radicals of the metalloporphyrins.     

Atmospheric chemistry of CF3CH=CH2 and C4F9CH=CH2: products of the gas-phase reactions with Cl atoms and OH radicals

FTIR-smog chamber techniques were used to study the products of the Cl atom and OH radical initiated oxidation of CF3CH=CH2 in 700 Torr of N2/O2, diluent at 296 K. The Cl atom initiated oxidation of CF3CH=CH2 in 700 Torr of air in the absence of NOx gives CF3C(O)CH2Cl and CF3CHO in yields of 70+/-5% and 6.2+/-0.5%, respectively. Reaction with Cl atoms proceeds via addition to the >C=C< double bond (74+/-4% to the terminal and 26+/-4% to the central carbon atom) and leads to the formation of CF3CH(O)CH2Cl and CF3CHClCH2O radicals. Reaction with O2 and decomposition via C-C bond scission are competing loss mechanisms for CF3CH(O)CH2Cl radicals, kO2/kdiss=(3.8+/-1.8)x10(-18) cm3 molecule-1. The atmospheric fate of CF3CHClCH2O radicals is reaction with O2 to give CF3CHClCHO. The OH radical initiated oxidation of CxF2x+1CH=CH2 (x=1 and 4) in 700 Torr of air in the presence of NOx gives CxF2x+1CHO in a yield of 88+/-9%. Reaction with OH radicals proceeds via addition to the >C=C< double bond leading to the formation of CxF2x+1C(O)HCH2OH and CxF2x+1CHOHCH2O radicals. Decomposition via C-C bond scission is the sole fate of CxF2x+1CH(O)CH2OH and CxF2x+1CH(OH)CH2O radicals. As part of this work a rate constant of k(Cl+CF3C(O)CH2Cl)=(5.63+/-0.66)x10(-14) cm3 molecule-1 s-1 was determined. The results are discussed with respect to previous literature data and the possibility that the atmospheric oxidation of CxF2x+1CH=CH2 contributes to the observed burden of perfluorocarboxylic acids, CxF2x+1COOH, in remote locations.     

Specific isolation of N-terminal fragments from proteins and their high-fidelity de novo sequencing

A new method to determine N-terminal amino acid sequences of multiple proteins at low pmol level by a parallel processing has been developed. The method contains the following five steps: (1) reduction, S-alkylation and guanidination for targeted proteins; (2) coupling with sulfosucccimidyl-2-(biotinamido)ethyl-1,3-dithiopropionate(sulfo-NHS-SS-biotin) to N(alpha)-amino groups of proteins; (3) digestion of the modified proteins by an appropriate protease; (4) specific isolation of N-terminal fragments of proteins by affinity capture using the biotin-avidin system; (5) de novo sequence analysis of peptides by MALDI-TOF-/MALDI-TOF-PSD mass spectrometry with effective utilization of the CAF (chemically assisted fragmentation) method.1 This method is also effective for N-terminal sequencing of each protein in a mixture of several proteins, and for sequencing components of a multiprotein complex. It is expected to become an essential proteomics tool for identifying proteins, especially when used in combination with a C-terminal sequencing method.     

Synthesis of phenyl furyl sulfides and phenyl furyl ethers by nucleophilic substitution of nitrofurans

Phenyl furyl sulfides ( 3a‐j ) and phenyl furyl ethers ( 3k‐n ), which are useful in synthesizing furocondensed 3‐ring compounds, can be synthesized by nucleophilic substitution of nitrofurans having electron withdrawal groups. In our experiments using 5‐nitrofurans having electron withdrawal groups ( 2a‐i ), nucleophilic substitution readily occurred with the benzenethiolate anion of thiosalicylic acid ( 1a ), the benzenethiolate anion of thiosalicylate ester ( 1b ), and the phenylate anions of salicylate esters ( 1c‐d ) to yield phenyl furyl sulfides ( 3a‐j ) and phenyl furyl ethers ( 3k‐n ).