用太赫兹时域光谱法检测沙粒中的微量原油

由于太赫兹波对极性物质有很高的灵敏度,因此可以利用太赫兹时域光谱技术检测沙粒中含有的微量原油。将微量的原油浓度与太赫兹衰减系数之间建立起线性模型。同时引入有效介质理论来证实太赫兹介电常数与原油含量低于200 ppm之间的线性关系。结果表明,太赫兹时域光谱技术可以成为检测沙粒中微量原油泄漏的有效方法。     

Development and Validation of the UPLC-DAD Methodology for the Detection of Triterpenoids and Phytosterols in Fruit Samples of Vaccinium macrocarpon Aiton and Vaccinium oxycoccos L.

Cranberries are used in the production of medicinal preparations and food supplements, which highlights the importance of triterpene compounds determination in cranberry fruit raw material. The aim of our study was to develop and validate for routine testing suitable UPLC-DAD methodology for the evaluation of triterpene acids, neutral triterpenoids, phytosterols, and squalene content in cranberry samples. The developed and optimized UPLC-DAD methodology was validated according to the guidelines of the International Council for Harmonization (ICH), evaluating the following parameters: range, specificity, linearity (R² > 0.999), precision, LOD (0.27–1.86 µg/mL), LOQ (0.90–6.18 µg/mL), and recovery (80–110%). The developed and validated technique was used for the evaluation of triterpenic compounds in samples of Vaccinium macrocarpon and Vaccinium oxycoccos fruits, and their peels, pulp and seeds. The studied chromatogram profiles of Vaccinium macrocarpon and Vaccinium oxycoccos were identical but differed in the areas of the analytical peaks. Ursolic acid was the dominant compound in fruit samples of Vaccinium macrocarpon and Vaccinium oxycoccos. The highest amounts of triterpenic compounds were detected in the cranberry peels samples. The developed method for the detection of triterpene compounds can be applied in further studies for routine testing on the qualitative and quantitative composition of fruit samples of Vaccinium macrocarpon and Vaccinium oxycoccos species and cultivars.     

Process Optimization of Phytoantioxidant and Photoprotective Compounds from Carob Pods (Ceratonia siliqua L.) Using Ultrasonic Assisted Extraction Method

The current study first describes the extraction of phytoantioxidant polyphenols from Carob byproducts (pods) using maceration and heating-assisted extraction as traditional methods and ultrasonic-assisted extraction (UAE) as an innovative method to determine the most efficient extraction process in terms of four targeted responses: total phenolic content (TPC), antioxidant activities (TAC and DPPH), and photoprotective properties as measured by the sun protection factor (SPF). Second, we used response surface methodology (RSM) with a central composite rotatable design (CCDR) approach to investigate the influence of process variables (extraction time, extraction temperature, and solvent concentration) on UAE, which was found to be the most effective extraction technique in our study. Carob byproduct extracts had a TPC ranging from 6.21 to 21.92 mg GAE/g dw, a TAC ranging from 22.00 to 49.30 mg AAE/g dw, DPPH scavenging activity ranging from 56.35 to 90.50%, and SPF values ranging from 8.62 to 22.37. The optimal UAE conditions for maximum TPC, TAC, DPPH, and SPF responses were determined to be 38.90% ethanol, 53.90 °C, and 50.92 min. Using Carob as a source for sustainable and bioactive products in conjunction with optimized UAE is a promising contribution to the cosmetic industry that will help to strengthen the concept of environmentally-friendly “green chemistry”. Given that Carob pulp or seeds are considered food byproducts, the research presented here encourages the use of these agri-food waste materials in cosmetics.     

Stable Phase Retrieval in Infinite Dimensions

Foundations of Computational Mathematics - The problem of phase retrieval is to determine a signal $$f\in \mathcal {H}$$ , with $$ \mathcal {H}$$ a Hilbert space, from intensity measurements...     

New eco-friendly procedure for the synthesis of 4-arylmethylene-isoxazol-5(4H)-ones catalyzed by pyridinium p-toluenesulfonate (PPTS) in aqueous medium

In this work we describe a new, highly efficient method for the synthesis of 3-methyl-4-arylmethylidene-isoxazol-5(4H)-one derivatives by a three-component reaction between aromatic aldehydes, ethyl acetoacetate, and hydroxylamine hydrochloride under the influence by PPTS as a low-toxicity, inexpensive, commercially available and easy to handle catalyst. The advantages of this procedure are good yields, short reaction times, simplicity of implementation, and respect of the environment.     

Asymmetric synthesis of all the known phlegmarine alkaloids

The asymmetric synthesis of all four of the known natural phlegmarines and one synthetic derivative has been accomplished in 19-22 steps from 4-methoxy-3-(triisopropylsilyl)pyridine. Chiral N-acylpyridinium salt chemistry was used twice to set the stereocenters at the C-9 and C-2' positions of the phlegmarine skeleton. Key reactions include the use of a mixed Grignard reagent for the second N-acylpyridinium salt addition, zinc/acetic acid reduction of a complex dihydropyridone, and a von Braun cyanogen bromide N-demethylation of a late intermediate. These syntheses confirmed the absolute stereochemistry of all of the known phlegmarines.     

Gas-phase synthesis and characterization of heteroleptic divalent germanium compounds by FVT/UV-PES

The flash vacuum thermolysis/UV photoelectron spectroscopic (FVT/UV-PES) technique has been applied for the synthesis of three cyclic germanediyls containing oxo-thio, oxo-amino, and thio-amino substitution at germanium. The three compounds (4b, 5b and 6b) were prepared from the corresponding 3,4-dimethyl-1-germacyclopent-3-enes (4a, 5a and 6a) by thermal cheletropic elimination, and the photoelectron spectra of both sets of molecules were measured. The course of the thermolysis reactions has also been confirmed by mass spectrometric methods and the results of chemical trapping experiments. The assignment of the PE spectral bands for the two series of molecules has been carried out with the aid of time dependent DFT (TD-DFT) and outer valence green’s function (OVGF) calculations. The results indicate that the strong σ-withdrawing effect of oxygen and the strong π-donating effect of nitrogen are the two main factors affecting the electronic structures of these germylene derivatives.     

Cu(II) bromide catalyzed oxidation of aldehydes and alcohols

A variety of aromatic, aliphatic and conjugated aldehydes and alcohols were transformed to the corresponding carboxylic acids and ketones with a quantitative conversion in high yields with 70% t‐BuOOH solution in water in the presence of catalytic (5 mol%) amounts of CuBr₂ under room temperature conditions. The conversion of 4‐methoxybenzaldehyde to 4‐methoxybenzoic acid is extremely facile in MeCN at ambient temperature in the presence of 5 mol% CuBr₂ and 2 equiv. 70% t‐BuOOH (water) as the oxidant. Oxidation with t‐BuOOH (water) alone in MeCN was found to be negligible. The scope of our catalytic system is applicable for a wide range of aromatic, conjugated and aliphatic substrates. These aldehydes were converted to the corresponding carboxylic acids in good isolated yields in reasonable times. It is pertinent to mention here that mild halogenic oxidants like hypochlorites, chlorites and NBS are not suitable for substrates with electron‐rich aromatic rings, olefinic bonds and secondary hydroxyl groups. Substitutions at different positions on the phenyl ring do not hinder the reaction, although the reaction time is affected. Oxidation of α,β unsaturated derivatives resulted in the formation of the expected acid in good yield. In addition, the transformation of secondary alcohols to ketones is extremely facile. No recemization was observed for menthone. This method possesses a wide range of capabilities since it can be used with other functional groups which may not tolerate oxidative conditions, involves fairly simple method for work‐up, exhibits chemoselectivity and proceeds under ambient conditions. The resulting products are obtained in good yields within reasonable time. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and characterizations of new isotactic homopolyesters,statistical and block copolyesters derived of poly((S)‐3,3‐dimethylmalic acid) via the lactone route

This article presents the synthesis of a new family of synthetic isotactic polyesters derived from poly((S)‐3,3‐dimethylmalic acid) (PDMMLA). These polyesters are prepared via the lactone route bearing functionalized groups in its main or side chain. The aim of this work is twofold: metabolism and stereochemistry. First, the synthesis of these new polyesters is chosen to provide biodegradable polyesters biocompatible and bioassimilable by the human body. Next, the molecular chain of this family contains a stereogenic center in the aim to provide 100% isotactic homopolymers and copolymers (statistical and block). Finally, these polymers have been characterized by several analytical techniques: FTIR, ¹H and ¹³C NMR, SEC, DSC, and TGA. The greatest importance will be given to the ¹³C NMR and DSC to principally confirm the stereoregularity and crystallinity of these stereopolyesters. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1495–1507