Synthesis of new pyrimidine-containing compounds: 5-(2-(alkylamino)-1,3-dioxo-2,3-dihydro-1H-inden-2-yl)-6-hydroxypyrimidine-2,4(1H,3H)-dione derivatives

Molecular Diversity - In this study, the one-pot reaction between primary amines, 1,1-bis-(methylthio)-2-nitroethene, ninhydrin, and barbituric acid as an enolizable C–H-activated compound...     

Anisotropic solutions for a holographic heavy-quark model with an external magnetic field

Theoretical and Mathematical Physics - We find a solution of the black hole type for a five-dimensional fully anisotropic holographic model for heavy quarks. The model is described by the Einstein...     

Restructuring Metal–Organic Frameworks to Nanoscale Bismuth Electrocatalysts for Highly Active and Selective CO2 Reduction to Formate

Recently, a large number of nanostructured metal‐containing materials have been developed for the electrochemical CO₂ reduction reaction (eCO₂RR). However, it remains a challenge to achieve high activity and selectivity with respect to the metal load due to the limited concentration of surface metal atoms. Here, it is reported that the bismuth‐based metal–organic framework Bi(1,3,5‐tris(4‐carboxyphenyl)benzene), herein denoted Bi(btb), works as a precatalyst and undergoes a structural rearrangement at reducing potentials to form highly active and selective catalytic Bi‐based nanoparticles dispersed in a porous organic matrix. The structural change is investigated by electron microscopy, X‐ray diffraction, total scattering, and spectroscopic techniques. Due to the periodic arrangement of Bi cations in highly porous Bi(btb), the in situ formed Bi nanoparticles are well‐dispersed and hence highly exposed for surface catalytic reactions. As a result, high selectivity over a broad potential range in the eCO₂RR toward formate production with a Faradaic efficiency up to 95(3)% is achieved. Moreover, a large current density with respect to the Bi load, i.e., a mass activity, up to 261(13) A g^?1 is achieved, thereby outperforming most other nanostructured Bi materials.     

Anisotropy of the Surface Energy and Work Function of IIB Metals

Technical Physics - On the basis of electron-statistical method of calculation of the surface energy of metals, a technique for estimating the electron work function of hexagonal and rhombohedral...     

Dead-time optimisation with reducing voltage distortion for nine-switch inverter

Nine-switch inverter with two sets of three-phase outputs is an improved topology proposed in place of the 12-switch back-to-back converters and has therefore attracted much attention in recent years. This inverter can be used with two conventional pulse width modulation approaches: different frequency and the constant frequency. One disadvantage of using this modulation method is the possibility of short-circuits in the legs (shoot-through), which decreases the reliability of converter and system. This paper presents a new modulation technique, in which switching pulses of nine-switch inverter are produced by not only the original carrier signals but also through two auxiliary carrier signals. In this method, adjustable three-phase voltages are produced in the inverter’s terminals, and so there is no possibility of any shoot-through in the inverter’s legs. The suggested reliable modulation approach does not rely on any information about the load polarity, as switching is performed by a simple and reliable algorithm. The result is the considerably better waveform quality of the output voltages in comparison with other methods. To verify the analysis, an experimental platform based on DSP is built. The simulation and experimental results are given to demonstrate the effectiveness and feasibility of this new approach.     

Dysarthric speaker identification with different degrees of dysarthria severity using deep belief networks

Dysarthria is a degenerative disorder of the central nervous system that affects the control of articulation and pitch; therefore, it affects the uniqueness of sound produced by the speaker. Hence, dysarthric speaker recognition is a challenging task. In this paper, a feature-extraction method based on deep belief networks is presented for the task of identifying a speaker suffering from dysarthria. The effectiveness of the proposed method is demonstrated and compared with well-known Mel-frequency cepstral coefficient features. For classification purposes, the use of a multi-layer perceptron neural network is proposed with two structures. Our evaluations using the universal access speech database produced promising results and outperformed other baseline methods. In addition, speaker identification under both text-dependent and text-independent conditions are explored. The highest accuracy achieved using the proposed system is 97.3%.     

Notes on the Syk Model in Real Time

We discuss a nonperturbative formulation of the Sachdev–Ye–Kitaev (SYK) model. The partition function of the model can be represented as a well-defined functional integral over Grassmann variables in Euclidean time, but it diverges after the transformation to fermion bilocal fields. We note that the generating functional of the SYK model in real time is well defined even after the transformation to bilocal fields and can be used for nonperturbative investigations of its properties. We study the SYK model in zero dimensions, evaluate its large-N expansion, and investigate phase transitions.     

On some subsets of Schechter's essential spectrum of a matrix operator and application to transport operator

This paper is devoted to the investigation of the essential approximate point spectrum and the essential defect spectrum of a 2 × 2 block operator matrix on a product of Banach spaces. The obtained results are applied to a two‐group transport operators with general boundary conditions in the Banach space L_p ([–a, a ] × [–1, 1]) × L_p ([–a, a ] × [–1, 1]), a > 0, p ≥ 1 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gauge equivalence of Tachyon solutions in the cubic Neveu—Schwarz string field theory

We construct a simple analytic solution of the cubic Neveu—Schwarz (NS) string field theory including the GSO(-) sector. This solution is analogous to the Erler—Schnabl solution in the bosonic case and to the solution in the pure GSO(+) case previously proposed by one of us. We construct exact gauge transformations of the new solution to other known solutions for the NS string tachyon condensation. This gauge equivalence manifestly supports the previous observation that the Erler solution for the pure GSO(+) sector and our solution containing both the GSO(+) and the GSO(-) sectors have the same value of the action density.