Weyl Invariance and Spurious Black Hole in Two-Dimensional Dilaton Gravity

In two-dimensional dilaton gravity theories, there may exist a global Weyl invariance which makes black hole spurious. If the global invariance and the local Weyl invariance of the matter coupling are intact at the quantum level, there is no Hawking radiation. We explicitly verify the absence of anomalies in these symmetries for the model proposed by Callan, Giddings, Harvey and Strominger. The crucial observation is that the conformal anomaly can be cohomologically trivial and so not truly anomalous in such dilaton gravity models.Comment: 28 pages, KANAZAWA-93-0

Symmetry-adapted HAM/3 method and its application to some symmetric molecules

The semiempirical HAM/3 method developed by Lindholm and coworkers about two decades ago has been known to have a deficiency that splits energies for the degenerate energy states. We have recently proposed a group-theoretical approach to remedy the internally broken symmetry of the HAM/3 Hamiltonians. In this paper, we present some results of its application to various small molecules with symmetry Td, C3v, and D3h. The proposed scheme gives correct degeneracy for these molecules.O método semi-empírico HAM/3, desenvolvido por Lindholm e colaboradores há mais de duas décadas, tem uma deficiência. As energias de excitação calculadas por HAM/3 para estados degenerados são desdobradas. Recentemente foi proposto um método para corrigir esta deficiência. Apresentamos aqui resultados de aplicações deste novo método para algumas moléculas com simetria Td, C3v e D3h. O esquema proposto apresenta a degenerescência correta para as moléculas estudadas.445449Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Biphenyl-Derived Phosphepines as Chiral Nucleophilic Catalysts: Enantioselective [4+1] Annulations To Form Functionalized Cyclopentenes

Because of the frequent occurrence of cyclopentane subunits in bioactive compounds, the development of efficient catalytic asymmetric methods for their synthesis is an important objective. Introduced herein is a new family of chiral nucleophilic catalysts, biphenyl-derived phosphepines, and we apply them to an enantioselective variant of a useful [4+1] annulation. A range of one-carbon coupling partners can be employed, thereby generating cyclopentenes which bear a fully substituted stereocenter [either all-carbon or heteroatom-substituted (sulfur and phosphorus)]. Stereocenters at the other four positions of the cyclopentane ring can also be introduced with good stereoselectivity. An initial mechanistic study indicates that phosphine addition to the electrophilic four-carbon coupling partner is not the turnover-limiting step of the catalytic cycle

Investigating the Generalizability of Deep Learning-based Clone Detectors

The generalizability of Deep Learning (DL) models is a significant challenge, as poor generalizability indicates that the model has overfitted to the training data and is not able to generalize to new data. Despite numerous DL-based clone detectors emerging in recent years, their generalizability has not been thoroughly assessed. This study investigates the generalizability of three DL-based clone detectors (CCLearner, ASTNN, and CodeBERT) by comparing their detection accuracy on different training and testing clone benchmarks. The results show that all three clone detectors do not generalize well to new data and there is a strong relationship between clone types and generalizability for CCLearner and ASTNN.Choi E., Fuke N., Fujiwara Y., et al. Investigating the Generalizability of Deep Learning-based Clone Detectors. IEEE International Conference on Program Comprehension 2023-May, 181 (2023); https://doi.org/10.1109/ICPC58990.2023.00032

Phosphine-Catalyzed Enantioselective Intramolecular [3+2] Annulations To Generate Fused Ring Systems

Substantial progress has been described in the development of asymmetric variants of the phosphine-catalyzed intermolecular [3+2] annulation of allenes with alkenes; however, there have not been corresponding advances for the intramolecular process, which can generate a higher level of complexity (an additional ring and stereocenter(s)). In this study, we describe the application of chiral phosphepine catalysts to address this challenge, thereby providing access to useful scaffolds that are found in bioactive compounds, including diquinane and quinolin-2-one derivatives, with very good stereoselectivity. The products of the [3+2] annulation can be readily transformed into structures that are even more stereochemically rich. Mechanistic studies are consistent with β addition of the phosphepine to the allene being the turnover-limiting step of the catalytic cycle, followed by a concerted [3+2] cycloaddition to the pendant olefin

A Small Tokamak “NOVA II”

A small tokamak, NOVA II, has been designed and constructed. The major radius is 30 cm, the minor radius 6 cm and the maximum toroidal field 15 kG. The device has a removable shell assembly for studying the stabilizing effect of a conductive shell. The basic concept of design and the specifications of the principal components are described. In preliminary experiments, stable discharge was maintained for 15 msec or longer. The electron temperatures measured by diamagnetism and conductivity are both above 100 eV. An electron density of 1-2×10¹³ cm⁻³ was observed by a 6 mm microwave interferometer. Spectroscopy of impurity lines and intensity measurement of hard X-ray radiation are also described

分子動力学法を用いた生体高分子のトリチウム誘起壊変 シミュレーションと精度評価のための実験系の構築

トリチウムの生体への影響は，トリチウム由来の線の飛程が水中や細胞中で数ミクロン程度と短いため，外部被ばくが問題となることはなく，内部被ばくに対する防護が重要となってくる．国内外の研究者によりマウスなどを用いての研究など同分野の研究は広く行われてきている．一方，我々は現実の生体そのものの階層ではなく，原子分子レベルの階層に絞り，トリチウムが生体分子（DNA）へ与える影響を分子動力学シミュレーションで解き明かすと共に，それにより生体分子の損傷機構解明をめざしてきた．さらに，シミュレーションと相補的に，蛍光顕微鏡を用いたDNA 一分子観察法によりトリチウム水中でのDNA の二本鎖切断メカニズムの測定も行ってきている．このような研究の試みは，複雑な生命体そのものに短絡的に結びつけるには，いまだ隔たりがあるが，生体分子そのもののトリチウム影響の必要な基礎情報の蓄積をめざすものである．このように核融合研究で培ってきたシミュレーション技法・測定技法を用いた「トリチウムの影響評価」の試みを紹介する