托卡马克真空室内线圈水冷管道接头强化二次流的数值研究

基于计算流体力学(CFD)理论，研究了不同曲率半径的螺旋导流片的托卡马克真空室内线圈水冷管道接头。利用湍流数值模拟方法，分析了线圈管道接头导流片曲率半径比、冷却水入口流速对线圈管道内流体平均雷诺数分布的影响。结果表明，不同导流片曲率半径比的线圈管道内的流体雷诺数分布曲线相似，平均雷诺数随入口流速的增加而增大，管道接头出口雷诺数随导流片曲率半径比的增大而减小，导流片曲率半径比小的管接头更适用于线圈水冷曲线管的二次流强化。此外，还为导流片曲率半径比为0.2的管接头拟合了管接头出口雷诺数与入口流速的关系式，为进一步研究类似于托卡马克真空室内线圈管道的曲线管接头的二次流强化提供理论基础。     

Comparison of two cold atmospheric pressure plasma jet configurations in argon

The present study compares the operation of two cold atmospheric plasma jet (CAPJ) configurations: needle-to-cylinder electrode configuration (CAPJ I) and single high-voltage cylinder electrode around the quartz tube (CAPJ II). The CAPJs were operated in argon flowing through a quartz capillary with 0.5-mm inner diameter into the ambient air, and the plasma was generated by sinusoidal kHz frequency AC power supplies. The main emphasis of the study was on the mechanism of the initiation of ionization waves for these two configurations. For both CAPJs, there appeared several ionization waves during one half-period of the applied voltage waveform, and the number of ionization waves increased at higher voltage amplitudes. However, we discovered marked differences in the initiation of the ionization waves for two different CAPJ configuration. The applied voltage controlled the initiation of consecutive ionization waves, which propagated from the grounded electrode towards the tube orifice in CAPJ I. In the case of CAPJ II, certain time had to pass for the initiation of a new ionization wave, and subsequent ionization waves within the same half-period started at the tube orifice. In addition to the differences in the initiation of the ionization waves, we observed that the CAPJ I was ignited and sustained at lower voltages, while CAPJ II produced a longer plasma jet. The observed advantages and deficiencies of investigated CAPJ configurations point out their potential in different applications.     

Spectral analysis of Pk Finite Element matrices in the case of Friedrichs–Keller triangulations via Generalized Locally Toeplitz technology

In the present article, we consider a class of elliptic partial differential equations with Dirichlet boundary conditions and where the operator is div(?a( x )?·), with a continuous and positive over $\stackrel{￣}{\mathrm{\Omega }}$, Ω being an open and bounded subset of ${\mathbb{R}}^d$, d≥1. For the numerical approximation, we consider the classical ${\mathbb{P}}_k$ Finite Elements, in the case of Friedrichs–Keller triangulations, leading, as usual, to sequences of matrices of increasing size. The new results concern the spectral analysis of the resulting matrix‐sequences in the direction of the global distribution in the Weyl sense, with a concise overview on localization, clustering, extremal eigenvalues, and asymptotic conditioning. We study in detail the case of constant coefficients on Ω=(0,1)² and we give a brief account in the more involved case of variable coefficients and more general domains. Tools are drawn from the Toeplitz technology and from the rather new theory of Generalized Locally Toeplitz sequences. Numerical results are shown for a practical evidence of the theoretical findings.     

Effective intervals and regular Dirichlet subspaces

It is shown in Li and Ying (2019) that a regular and local Dirichlet form on an interval can be represented by so-called effective intervals with scale functions. This paper focuses on how to operate on effective intervals to obtain regular Dirichlet subspaces. The first result is a complete characterization for a Dirichlet form to be a regular subspace of such a Dirichlet form in terms of effective intervals. Then we give an explicit road map how to obtain all regular Dirichlet subspaces from a local and regular Dirichlet form on an interval, by a series of intuitive operations on the effective intervals in the representation above. Finally applying previous results, we shall prove that every regular and local Dirichlet form has a special standard core generated by a continuous and strictly increasing function.     

Single crystal X-ray of 1-[(1,2,4-triazole-4-yl)imino]diacetyl monoxime (L) as a novel triazole and the characterization and biological studies of its chelates of Co2+, Pd2+, and Fe3+

A novel and efficient synthesis of 1-[(1,2,4-triazole-4-yl)imino]diacetyl monoxime ( L ) is described. The advantages of this method are that it is inexpensive, the starting reactants are readily available, and it has good yield and short reaction times. The hull of the product was suggested by elemental analyses, spectral and single crystal X-ray. Novel Co ²⁺ , Pd²⁺, and Fe ³⁺ chelates derived from L were characterized by Fourier transform infrared spectroscopy, suggesting that L acts as bidentate via the two azomethine groups. Tetrahedral geometry for Fe³⁺ and Co²⁺ and square-planar geometry around the Pd²⁺ chelate were suggested depending on the spectral and magnetic data. The results of density functional theory were applied to illustrate the geometry of L towards the metal ions. Coats–Redfern and Horowitz–Metzger methods were applied to investigate the kinetic and thermodynamic parameters of the chelates. Cyclic voltammetry was carried out to study the stability of the Co²⁺ and Fe³⁺ chelates. L and its complexes were tested against three types of cancer cells, antibacterial and antifungal.     

Role of anti-inflammatory interventions in high-fat-diet-induced obesity

Lipotoxicity is defined as deposition of excess fat associated with an inflammatory response. Metabolomic analysis of fatty acids (FAs) can be a marker of silent inflammation. ω3-Enriched diet, celecoxib, and safranal may have a protective anti-inflammatory role. In this work, total FAs extracted from red blood cells and arachidonic acid-to-eicosapentaenoic acid (AA-to-EPA) ratios were assessed using GC–MS assay in single-ion monitoring mode. The study was conducted on 64 male rats divided into eight groups: I, controls; II, rats received high-fat diet (HFD), III, rats received ω-6-enriched HFD; IV, rats received ω-3-enriched HFD; V, rats received celecoxib with HFD; VI, rats received safranal with HFD; VII and VIII, rats received celecoxib and safranal with ω-3 HFD, respectively. GC–MS Gas chromatography Mass spectrometry was performed for analysis of fatty acid methyl ester. Enzyme-linked immunosorbent assay was used to analyze serum interleukin-6 (IL-6) and transforming growth factor-beta 1 (TGF-β1) concentrations. A statistically significant decrease of AA-to-EPA ratio was observed in group VII when compared with the groups receiving HFDs. This group also showed the lowest serum IL-6 level and highest TGF-β1 level. In conclusion, ω3-enriched diet along with drugs (e.g. celecoxib) and herbal medications (e.g. safranal) may have an anti-inflammatory effect in lipotoxicity. GC–MS with single-ion monitoring is valid for the analysis of FAs.     

A molecular fluorophore in citric acid/ethylenediamine carbon dots identified and quantified by multinuclear solid-state nuclear magnetic resonance

The composition of fluorescent polymer nanoparticles, commonly referred to as carbon dots, synthesized by microwave-assisted reaction of citric acid and ethylenediamine was investigated by ¹³C, ¹³C{¹H}, ¹H─¹³C, ¹³C{¹⁴N}, and ¹⁵N solid-state nuclear magnetic resonance (NMR) experiments. ¹³C NMR with spectral editing provided no evidence for significant condensed aromatic or diamondoid carbon phases. ¹⁵N NMR showed that the nanoparticle matrix has been polymerized by amide and some imide formation. Five small, resolved ¹³C NMR peaks, including an unusual ═CH signal at 84 ppm (¹H chemical shift of 5.8 ppm) and ═CN₂ at 155 ppm, and two distinctive ¹⁵N NMR resonances near 80 and 160 ppm proved the presence of 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (IPCA) or its derivatives. This molecular fluorophore with conjugated double bonds, formed by a double cyclization reaction of citric acid and ethylenediamine as first shown by Y. Song, B. Yang, and coworkers in 2015, accounts for the fluorescence of the carbon dots. Cross-peaks in a ¹H─¹³C HETCOR spectrum with brief ¹H spin diffusion proved that IPCA is finely dispersed in the polyamide matrix. From quantitative ¹³C and ¹⁵N NMR spectra, a high concentration (18 ± 2 wt%) of IPCA in the carbon dots was determined. A pronounced gradient in ¹³C chemical-shift perturbations and peak widths, with the broadest lines near the COO group of IPCA, indicated at least partial transformation of the carboxylic acid of IPCA by amide or ester formation.     

Measurement of the hydrodynamic radii of PEE-G dendrons by diffusion spectroscopy on a benchtop NMR spectrometer

Benchtop nuclear magnetic resonance (NMR) spectroscopy is a useful tool for the rapid determination of the self-diffusion coefficient and the hydrodynamic radius of dendrons. The self-diffusion coefficients of the first four generations of poly ethoxy ethyl glycinamide (PEE-G) dendrons are measured by diffusion-ordered spectroscopy (DOSY) on a benchtop NMR equipped with diffusion gradient coils. The hydrodynamic radii of the dendrons are calculated via the Stokes–Einstein equation. The effects of solvent and pH are determined with the hydrodynamic radius increasing with generation and decreasing upon neutralization of an acidic solution. These measurements provide valuable information for biological and pharmaceutical applications of dendrons.     

Reversible Ultra-Slow Crystal Growth of Mixed Lead Bismuth Perovskite Nanocrystals: The Presence of Dynamic Capping

An ultra-slow crystal growth over a period of 24 h of a newly synthesized CH₃NH₃Pb_1/2Bi_1/3I₃ perovskite (MPBI) nanocrystal in non-polar toluene medium is reported here. From several spectroscopic techniques as well as from TEM analysis we found that the size of nanocrystals changes continuously with time, in spite of being capped by the ligands. Using a single molecular spectroscopic technique, we also found that this size change is not due to the stacking of nanocrystals but due to crystal growth. The notable temperature dependence and reversible nature of the nanocrystals growth is explained by the dynamic nature of the capping. The observed temperature-dependent ultra-slow growth is believed to be a pragmatic step towards controlling the size of perovskite NC in a systematic manner.     

Hermitian adjacency matrix of the second kind for mixed graphs

This contribution gives an extensive study on spectra of mixed graphs via its Hermitian adjacency matrix of the second kind (N-matrix for short) introduced by Mohar [25]. This matrix is indexed by the vertices of the mixed graph, and the entry corresponding to an arc from u to v is equal to the sixth root of unity $\omega =\frac{1+\mathbf{i}\sqrt{3}}{2}$ (and its symmetric entry is $\overline{\omega }=\frac{1?\mathbf{i}\sqrt{3}}{2}$); the entry corresponding to an undirected edge is equal to 1, and 0 otherwise. The main results of this paper include the following: equivalent conditions for a mixed graph that shares the same spectrum of its N-matrix with its underlying graph are given. A sharp upper bound on the spectral radius is established and the corresponding extremal mixed graphs are identified. Operations which are called two-way and three-way switchings are discussed–they give rise to some cospectral mixed graphs. We extract all the mixed graphs whose rank of its N-matrix is 2 (resp. 3). Furthermore, we show that if $M_G$ is a connected mixed graph with rank 2, then $M_G$ is switching equivalent to each connected mixed graph to which it is cospectral. However, this does not hold for some connected mixed graphs with rank 3. We identify all mixed graphs whose eigenvalues of its N-matrix lie in the range $(?\alpha ,\alpha )$ for $\alpha \in \{\sqrt{2},\sqrt{3},2\}$.