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91.
In 2002, Bollobás and Scott posed the following problem: for an integer and a graph G of m edges, what is the smallest f (k, m ) such that V (G ) can be partitioned into V 1,…,V k in which for all , where denotes the number of edges with both ends in ? In this paper, we solve this problem asymptotically by showing that . We also show that V (G ) can be partitioned into such that for , where Δ denotes the maximum degree of G . This confirms a conjecture of Bollobás and Scott. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 50, 59–70, 2017 相似文献
92.
Francisco W. Maciel-Silva Daniel Lachos-Perez Luz Selene Buller William G. Sganzerla Montserrat Prez Mauricio A. Rostagno Tania Forster-Carneiro 《Molecules (Basel, Switzerland)》2022,27(19)
The detection of analytes in complex organic matrices requires a series of analytical steps to obtain a reliable analysis. Sample preparation can be the most time-consuming, prolonged, and error-prone step, reducing the reliability of the investigation. This review aims to discuss the advantages and limitations of extracting bioactive compounds, sample preparation techniques, automation, and coupling with on-line detection. This review also evaluates all publications on this topic through a longitudinal bibliometric analysis, applying statistical and mathematical methods to analyze the trends, perspectives, and hot topics of this research area. Furthermore, state-of-the-art green extraction techniques for complex samples from vegetable matrices coupled with analysis systems are presented. Among the extraction techniques for liquid samples, solid-phase extraction was the most common for combined systems in the scientific literature. In contrast, for on-line extraction systems applied for solid samples, supercritical fluid extraction, ultrasound-assisted extraction, microwave-assisted extraction, and pressurized liquid extraction were the most frequent green extraction techniques. 相似文献
93.
Dr. Heyong Cheng Shuli Tang Tingyuan Yang Prof. Shiqing Xu Prof. Xin Yan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20034-20039
Microdroplet chemistry is attracting increasing attention for accelerated reactions at the solution–air interface. We report herein a voltage-controlled interfacial microreactor that enables acceleration of electrochemical reactions which are not observed in bulk or conventional electrochemical cells. The microreactor is formed at the interface of the Taylor cone in an electrospray emitter with a large orifice, thus allowing continuous contact of the electrode and the reactants at/near the interface. As a proof-of-concept, electrooxidative C−H/N−H coupling and electrooxidation of benzyl alcohol were shown to be accelerated by more than an order of magnitude as compared to the corresponding bulk reactions. The new electrochemical microreactor has unique features that allow i) voltage-controlled acceleration of electrochemical reactions by voltage-dependent formation of the interfacial microreactor; ii) “reversible” electrochemical derivatization; and iii) in situ mechanistic study and capture of key radical intermediates when coupled with mass spectrometry. 相似文献
94.
《无机化学与普通化学杂志》2018,644(6):367-375
The hydrogenation properties of the intermetallic compounds MgPd2 and Pd2Zn, crystallizing in the Co2Si type, were studied by in situ thermal analysis (DSC) under hydrogen pressure. Pd2Zn does not show any reaction with hydrogen while MgPd2 reversibly forms the hydride MgPd2H. Neutron diffraction on the deuterides reveals the compositions MgPd2D0.861(6) (ambient) and MgPd2D0.97(1) [308(2) K, 2.56(5) MPa deuterium] with hydrogen (deuterium) occupying distorted [MgPd5] octahedral voids. Quantum mechanical calculations support the structure models and show the hydrogenation to be exergonic for MgPd2 and endergonic for Pd2Zn. MgPd2H releases hydrogen under normal conditions or vacuum. Heating under hydrogen pressure leads first reversibly to MgPd2H≈0.2 and subsequently irreversibly to MgPd3H≈1 and MgH2. MgPd2, Pd2Zn, and MgPd2H were classified in a structure map. Trends of axial ratio changes upon hydrogenation of TiNiSi type and ZrBeSi type compounds are discussed. 相似文献
95.
Karen L. Kindle 《Applied biochemistry and biotechnology》1983,8(2):153-170
Thermostable α-amylases have application in a variety of industrial processes and enzymes from a substantial number of thermophilic
bacteria and fungi have been screened and characterized to varying degrees. The characteristics of these enzymes are summarized
in this review. The genetics of α-amylase production inBacillus subtilis is reviewed and classical and recombinant DNA approaches to increasing α-amylase production are discussed. 相似文献
96.
The applicability of the headspace coupled to mass spectrometry for evaluation of the sensory quality of virgin olive oil samples is presented. The volatiles of the oil are directly transferred from the sample vial to the detector without chromatographic separation. The mass spectrum obtained can be considered as a fingerprint of the oil sample and can be used for classification purposes. After a training step with samples previously qualified following the official method, a classification model was created using the supervised technique soft independent modeling of class analogy (SIMCA). Eight negative (rancid, winey-vinegary, muddy sediment, hay-wood, vegetable water, earthy, fusty and musty-humidity) and three principal positive attributes (fruity, bitter and pungent) have been included in this study. With them, a classification model consisting of two main classes (extra- and lampante-virgin olive oil) was constructed. In addition, the unsupervised technique cluster analysis permited the discrimination among oils with different negative attributes. The proposed procedure has been applied to the classification of commercial samples (as extra- or lampante-virgin olive oils) and the results were compared with those provided by the expert's panel with acceptable correlation. 相似文献
97.
Spectroscopic techniques have been finding increasing applications in the field of biomedicine especially in the field of disease diagnosis and monitoring in spite of the rapid emergence of several molecular biology based techniques. The significance of spectroscopy techniques and the possibility of using some of the underutilized regions of the electromagnetic radiations are discussed in this review. While previous reviews have already dealt with the potential of Fourier transform infrared spectroscopy-based (FTIR) techniques for clinical applications, the present review addresses the lacunae of the techniques along with its future trends that may make it a technique routinely applied in clinical settings. 相似文献
98.
Bisphenol-A polycarbonate films were irradiated with 86 MeV swift heavy nickel ions at varying fluences, ranging from 1 × 1011 to 1 × 1013 ions cm?2, under vacuum at room temperature, to analyze the induced electrical and thermal modifications. AC conductivity measurements and UV-visible spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) techniques were applied to analyze the changes. A significant, exponential increase in conductivity at higher frequency was observed with the increase of nickel ion fluence. UV-visible analysis corroborated the results of the AC conductivity measurement, revealing the increase in size of the carbon clusters embedded in the polymer network, with the increase of heavy ion fluence. FTIR analysis revealed the formation of alkene and alkyne end groups at higher doses, which further supported the suggestion that the variation in electrical properties induced by the ion irradiation of the polymer was due to development of a carbonaceous phase inside the polymer due to the irradiation. Thermal analysis, i.e., TGA and DSC patterns, showed that chain-scission was the leading phenomena in the heavy ion-irradiated polycarbonate samples, resulting in degradation of their thermal stability. 相似文献
99.
100.
Liping He 《计算数学(英文版)》2010,28(5):676-692
In this paper, we extend the reduced basis methods for parameter dependent problems to the parareal in time algorithm introduced by Lions et al. [12] and solve a nonlinear evolutionary parabolic partial differential equation. The fine solver is based on the finite element method or spectral element method in space and a semi-implicit Runge-Kutta scheme in time. The coarse solver is based on a semi-implicit scheme in time and the reduced basis approximation in space. Of[line-online procedures are developed, and it is proved that the computational complexity of the on-line stage depends only on the dimension of the reduced basis space (typically small). Parareal in time algorithms based on a multi-grids finite element method and a multi-degrees finite element method are also presented. Some numerical results are reported. 相似文献