Existence of positive periodic solutions for second-order functional differential equations

In this paper, we show the existence of positive $T$ -periodic solutions of second-order functional differential equations $u^{\prime \prime }(t)-\rho ^2u(t)+\lambda g(t)f(u(t-\tau (t)))=0,\ \ t\in \mathbb R , $ where $\rho >0$ is a constant, $g\in C(\mathbb R ,[0,\infty ))$ , $\tau \in C(\mathbb R ,\mathbb R )$ are $T$ -periodic functions, $f\in C([0,\infty ),[0,\infty ))$ and $\lambda $ is a positive parameter. Our approach based on global bifurcation theorem.     

Cost estimation algorithm and decision-making model for curriculum modification in educational organization

The decision about curriculum modification usually takes place at the knowledge level, mainly with consideration of individual academic staff competences and qualifications. However, traditional approaches to cost estimation of curriculum modification are focused on material resources only. In this paper we present a cost estimation method and decision model for curriculum modification in educational organizations. The proposed method works at the knowledge level and employs competence sets as knowledge representation models in educational organizations. Authors used the theory of hierarchical, multilevel systems in order to define the model of the decision-making process of curriculum modification and its dimension. Basing on this and also using a fuzzy competence model the cost estimation algorithm in the form of a group competences expansion algorithm is proposed. The algorithm focuses on the cost of staff competence expansion caused by the knowledge development process.     

Efficient glycosylation with glycosyl ortho-allylbenzoates as donors

Glycosylation reactions are significant as they provide access to model compounds that are useful for elucidating biochemical pathways. Herein, we describe the development of glycosyl ortho-alkynylbenzoates as novel, bench-top stable, and readily available glycosyl donors. Glycosylation is promoted by inexpensive trimethylsilyl triflate (TMSOTf) in combination with N-iodosuccinimide (NIS) under mild reaction conditions; hence, the novel glycosyl donors are promising reagents for the synthesis of glycosides.     

One-pot diastereoselective synthesis of tetrahydroepimino-benzo[b]azocines through sequential [3+2]-cycloaddition and Staudinger-aza-Wittig reactions

The one-pot synthesis of tetrahydro-epiminobenzo[b]azocines through a sequential 1,3-dipolar cycloaddition and intramolecular Staudinger-aza-Wittig reaction sequence is reported. This methodology provides a new and efficient approach for medium-sized and bridged nitrogen heterocyclic molecules.     

Efficient Synthesis of Spirooxindole Pyrrolones by a Rhodium(III)‐Catalyzed C−H Activation/Carbene Insertion/Lossen Rearrangement Sequence

A rhodium(III)‐catalyzed domino annulation of simple olefins with diazo oxindoles to give spirooxindole pyrrolone products is described. This reaction can be formally viewed as the result of an anomalous tandem C?H activation, carbene insertion, Lossen rearrangement, and a nucleophilic addition process. The potential utility of this reaction was further demonstrated by the late‐stage diversification of drug molecules.     

Organic Proton‐Buffer Electrode to Separate Hydrogen and Oxygen Evolution in Acid Water Electrolysis

Hydrogen production from water via electrolysis in acid is attracting extensive attention as an attractive alternative approach to replacing fossil fuels. However, the simultaneous evolution of H₂ and O₂ requires a fluorine‐containing proton exchange membrane to prevent the gases from mixing while using the same space to concentrate the gases, which significantly increases the cost and reduces the flexibility of this approach. Here, a battery electrode based on the highly reversible enolization reaction of pyrene‐4,5,9,10‐tetraone is first introduced as a solid‐state proton buffer to separate the O₂ and H₂ evolution of acidic water electrolysis in space and time, through which the gas mixing issue can be avoided without using any membrane. This process allows us to separately consider H₂ and O₂ production according to the variation in input power (e.g., the renewable energy) and/or the location for H₂ concentration, thus showing high flexibility for H₂ production.     

Bifunctional Phosphine Ligand Enabled Gold‐Catalyzed Alkynamide Cycloisomerization: Access to Electron‐Rich 2‐Aminofurans and Their Diels–Alder Adducts

By using biphenyl‐2‐ylphosphines functionalized with a remote tertiary amino group as a ligand, readily available acetylenic amides are directly converted into 2‐aminofurans devoid of any electron‐withdrawing and hence deactivating/stabilizing substituents. These highly electron‐rich furans have rarely been prepared, let alone applied in synthesis, because of their high reactivities and low stabilities associated with the electron‐rich nature of the furan ring. In this work, these reactive furans smoothly undergo either in situ intermolecular Diels–Alder reactions to deliver highly functionalized/substituted aniline products or intramolecular ones to furnish carbazole‐4‐carboxylates in mostly good to excellent yields. This work offers general and expedient access to this class of little studies electron‐rich furans and should lead to exciting opportunities for their applications.     

In Silico Structure-Guided Optimization and Molecular Simulation Studies of 3-Phenoxy-4-(3-trifluoromethylphenyl)pyridazines as Potent Phytoene Desaturase Inhibitors

A series of novel 3-phenoxy-4-(3-trifluoromethylphenyl)pyridazines 2–5 were designed, based on the structure of our previous lead compound 1 through the in silico structure-guided optimization approach. The results showed that some of these new compounds showed a good herbicidal activity at the rate of 750 g ai/ha by both pre- and post-emergence applications, especially compound 2a, which displayed a comparable pre-emergence herbicidal activity to diflufenican at 300–750 g ai/ha, and a higher post-emergence herbicidal activity than diflufenican at the rates of 300–750 g ai/ha. Additionally, 2a was safe to wheat by both pre- and post-emergence applications at 300 g ai/ha, showing the compound’s potential for weed control in wheat fields. Our molecular simulation studies revealed the important factors involved in the interaction between 2a and Synechococcus PDS. This work provided a lead compound for weed control in wheat fields.     

Mechanisms of a Cyclobutane-Fused Lactone Hydrolysis in Alkaline and Acidic Conditions

Searching for functional polyesters with stability and degradability is important due to their potential applications in biomedical supplies, biomass fuel, and environmental protection. Recently, a cyclobutane-fused lactone (CBL) polymer was experimentally found to have superior stability and controllable degradability through hydrolysis reactions after activation by mechanical force. In order to provide a theoretical basis for developing new functional degradable polyesters, in this work, we performed a detailed quantum chemical study of the alkaline and acidic hydrolysis of CBL using dispersion-corrected density functional theory (DFT-D3) and mixed implicit/explicit solvent models. Various possible hydrolysis mechanisms were found: B_AC2 and B_AL2 in the alkaline condition and A_AC2, A_AL2, and A_AL1 in the acidic condition. Our calculations indicated that CBL favors the B_AC2 and A_AC2 mechanisms in alkaline and acidic conditions, respectively. In addition, we found that incorporating explicit water solvent molecules is highly necessary because of their strong hydrogen-bonding with reactant/intermediate/product molecules.     

Electronic properties of polyoxometalate derivatives [(C2B9H11) M'M5O18]n‐ (M' = TiIV,MoVI, WVI; M = MoVI,WVI): Protonation,Electronic Spectra,and Redox Properties

Density functional theory is used to study the electronic structures and properties of Lindqvist‐type polyoxometalates‐supported organometallic compounds [LM'M₅O₁₈]^n– (L = [C₂B₉H₁₁]^2– (Cb), [C₅H₅]^– (Cp); M' = Ti^IV, Mo^VI, W^VI; M = Mo^VI, W^VI). [(Cb)M'M₅O₁₈]^n– are a series of novel compounds designed in this work, based on related experiment. The calculated results reveal that the Cb ligand is able to form a σ, 2π triple bond with M', which is similar to the bond character in [(Cp)M'M₅O₁₈]^n–. However, comparing with the protonation, electronic spectra and redox properties of [(Cp)M'M₅O₁₈]^n– and [M'M₅O₁₉]^n–, [(Cb)M'M₅O₁₈]^n– species show the advantageous electronic properties owning to the superior electron donating ability of the Cb ligand. © 2015 Wiley Periodicals, Inc.