Natural estrogens in dairy products: Determination of free and conjugated forms by ultra high performance liquid chromatography with tandem mass spectrometry

Natural estrogens are synthesized by mammals in different amounts depending on the developmental stage and pregnancy/lactation period, and they may pass into milk, where they are mostly present as glucuronated and sulfated forms. In modern dairy practices, about 75% of milk is produced from pregnant cows; therefore, the amount of hormones that may pass into milk could be of concern. While estrogen determination in milk has been investigated in depth, the individual determination of estrogens and their conjugated forms in dairy products has not been fully addressed. The aim of this work was to develop and assess a sensitive method, using the peculiar retention properties of graphitized carbon black, to extract natural free estrogens and their major conjugated metabolites, without any enzymatic cleavage, from yogurt, cheese, and butter. The free and conjugated estrogens were eluted in two distinct fractions from the solid‐phase extraction cartridge and analyzed separately by ultra high performance liquid chromatography coupled to tandem mass spectrometry. Recoveries were higher than 80% for all the three sample typologies. The highest matrix effects were observed for butter, which was richest in lipid content, but was below 30%. A survey on some commercial dairy products suggests that production processes decreased estrogen content.     

Effect of nonlinear electrodynamics on shadows of slowly rotating black holes

In this study, we investigate the effect of nonlinear electrodynamics on the shadows of charged, slowly rotating black holes with the presence of a cosmological constant. Rather than the null geodesic of the background black hole spacetime, the trajectory of a photon, as a perturbation of the nonlinear electrodynamic field, is governed by an effective metric. The latter can be derived by analyzing the propagation of a discontinuity of the electromagnetic waveform. Subsequently, the image of the black hole and its shadow can be evaluated using the backward ray-tracing technique. We explore the properties of the resultant black hole shadows of two different scenarios of nonlinear electrodynamics, namely, the logarithmic and exponential forms. In particular, the effects of nonlinear electrodynamics on the optical image are investigated, as well as the image's dependence on other metric parameters, such as the black hole spin and charge. The resulting black hole image and shadow display rich features that potentially lead to observational implications.     

Charged AdS black holes with finite electrodynamics in 4D Einstein-Gauss-Bonnet gravity

Using a modified expression for the electric potential in the context of T-duality [Gaete and Nicolini, Phys. Lett. B, 2022], we obtained an exact charged solution within the 4D Einstein-Gauss-Bonnet (4D EGB) theory of gravity in the presence of a cosmological constant. We show that the solution also exists in the regularized 4D EGB theory. Moreover, we point out a correspondence between the black hole solution in the 4D EGB theory and the solution in the non-relativistic Horava–Lifshitz theory. The black hole solution is regular and free from singularity. As a special case, we derive a class of well known solutions in the literature.     

显微共聚焦拉曼光谱结合群分析的黑色直液笔墨迹鉴别研究

黑色直液笔是一种新型书写工具,目前对该种笔墨迹的相关研究较少。为给文件检验工作中墨迹的分析提供新的参考依据,本实验使用显微共聚焦拉曼光谱技术,采集了30支不同品牌、型号的黑色直液笔墨迹光谱数据,进行Savitzky-Golay卷积平滑处理后,依据光谱图的拉曼位移及拉曼谱峰差异对墨迹进行初步分析。设置聚类方法为组间联接,区间距离测量方式为平方欧式距离,对采集的光谱数据进行群分析,将30支黑色直液笔墨迹样本分成了3类,并与品牌建立了相关联系;同时通过主成分分析验证了群分析的可靠性和准确性。研究表明,显微共聚焦拉曼光谱技术结合群分析方法可实现对黑色直液笔墨迹的无损分析及有效鉴别,该方法操作简便、结果准确,适用于法庭科学文件检验。     

Development of a method to screen and isolate xanthine oxidase inhibitors from black bean in a single step: Hyphenation of semipreparative liquid chromatography and stepwise flow rate countercurrent chromatography

Black bean, in which isoflavones are the main active constituent, also contains saponins and monoterpenes. Soybean isoflavone is a secondary metabolite that is formed during the growth of soybean; it exhibits antioxidant and cardiovascular activities and traces estrogen-like effects. In this study, black bean isoflavones were extracted with n-butanol, and ultrafiltration–liquid chromatography–mass spectrometry was used to screen their activity. Subsequently, the inhibitors were isolated and purified using semipreparative liquid chromatography and stepwise flow rate countercurrent chromatography. Thereafter, five active compounds were identified using mass spectrometry and nuclear magnetic resonance experiments. Finally, the inhibition types of the xanthine oxidase inhibitors were determined using enzymatic kinetic studies. The IC₅₀ values of daidzin, glycitein-7-O-glucoside, genistin, daidzein, and genistein were determined to be 35.08, 56.22, 30.76, 68.79, and 95.37 μg/mL, respectively. Daidzin, genistin, and daidzein exhibited reversible inhibition, whereas glycitein-7-O-glucoside and genistein presented irreversible inhibition. This novel approach, which was based on ultrafiltration–liquid chromatography–mass spectrometry and stepwise flow rate countercurrent chromatography, is a powerful method for screening and isolating xanthine oxidase inhibitors from complex matrices. The study of enzyme inhibition types is helpful for understanding the underlying inhibition mechanism. Therefore, a beneficial platform was developed for the large-scale production of bioactive and nutraceutical ingredients.     

Cysteine combined with carbon black as support for electrodeposition of poly (1,8-Diaminonaphthalene): Application as sensing material for efficient determination of nitrite ions

Poly 1,8-Diaminonaphtahlene/cysteine (poly 1,8-DAN/Cys) combined with carbon black (CB) nanoparticles are proposed as an excellent sensor for the detection of nitrite ions. To design the electrocatalyst, a simple approach consisting on drop-casting method was applied to disperse carbon black on the surface of glassy carbon electrode, followed by the immobilization of cysteine on the surface of CB nanoparticles. The electrochemical polymerization of 1,8-Diaminonaphthalene was conducted in acidic medium by using cyclic voltammetry. The prepared hybrid material was denoted poly 1,8-DAN /Cys/CB. Several methods were used to characterize the structural and electrochemical behavior of the reported hybrid material including Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), amperometry and differential pulse voltammetry (DPV). The prepared electrode displayed an outstanding electroactivity towards nitrite ions reflected by an enhancement in the intensity of the current and a decrease of the charge transfer resistance. Poly 1,8-DAN/Cys/CB displayed an excellent sensing performance towards the detection of nitrite with a very low detection limit of 0.25 µM. Two linear ranges of 1–40 µM and 20–210 µM when using amperometry and differential pulse voltammetry (DPV) were obtained respectively. This work highlights the simple preparation of a polymeric film rich in amine and thiol groups for nitrite detection.     

直接进样电热蒸发-原子荧光光谱法快速测定蒸馏酒中镉

为了快速低成本测定蒸馏酒中痕量重金属镉,利用钨丝电热蒸发器作为直接进样装置,与原子荧光光谱仪原子化器直接连接,构建了用于蒸馏酒中镉测定的直接进样原子荧光光谱检测系统(W-coil ETV-AFS),并对工作气体的气氛和流速、灰化和蒸发电压、样品承载量等参数进行了优化,建立了蒸馏酒中镉的直接进样快速检测方法。在最优条件下,Cd的检出限(LOD)为0.06μg/L(进样量为50μL),在0.5~100μg/L线性范围内回归系数(R²)为0.997;在5μg/L水平下,9个典型蒸馏酒样品的加标回收率在86.0%~116%,相对标准偏差RSD≤8.0%(n=3)。可以直接导入样品,无需复杂的前处理过程,具有良好的灵敏度、准确度和精密度,非常适合蒸馏酒中痕量镉的快速测定。     

Interface Amorphization of Two-Dimensional Black Phosphorus upon Treatment with Diazonium Salts

Two-dimensional (2D) black phosphorus (BP) represents one of the most appealing 2D materials due to its electronic, optical, and chemical properties. Many strategies have been pursued to face its environmental instability, covalent functionalization being one of the most promising. However, the extremely low functionalization degrees and the limitations in proving the nature of the covalent functionalization still represent challenges in many of these sheet architectures reported to date. Here we shine light on the structural evolution of 2D-BP upon the addition of electrophilic diazonium salts. We demonstrated the absence of covalent functionalization in both the neutral and the reductive routes, observing in the latter case an unexpected interface conversion of BP to red phosphorus (RP), as characterized by Raman, ³¹P-MAS NMR, and X-ray photoelectron spectroscopies (XPS). Furthermore, thermogravimetric analysis coupled to gas chromatography and mass spectrometry (TG-GC-MS), as well as electron paramagnetic resonance (EPR) gave insights into the potential underlying radical mechanism, suggesting a Sandmeyer-like reaction.     

利用地球上丰富的炭黑和NiS_2双助催化剂修饰提高CdS纳米片体系的可见光产氢活性(英文)

光催化产氢技术是目前解决能源和环境问题的最有潜力的方法之一,因此制备安全高效的光催化剂已成为目前的研究热点.在目前研究的各种光催化剂中,CdS光催化剂因为具有较窄的带隙(2.4 eV)和合适的导带位置,所以在可见光催化产氢领域受到广泛关注.然而,光生电子/空穴对易复合和光腐蚀作用极大地限制了CdS光催化剂的放大应用.因此,人们采用众多改性策略以提高CdS光催化剂的可见光产氢活性,其中构建CdS纳米结构和负载助催化剂被认为是最有效的方式.构建CdS纳米结构既可以缩短载流子的迁移路径,也可以减少CdS晶体中的缺陷.很多不同纳米结构的CdS光催化剂已经被开发,例如纳米线、纳米颗粒和纳米棒等.因为制备过程极为复杂繁琐,所以CdS纳米片的研究鲜见报道.本文采用乙酸鎘和硫脲为原材料,通过简单的溶剂热法合成了CdS纳米片.在CdS的各类助催化剂中,由于常用的Pt,Ag和Au等贵金属的高成本和低储量等问题严重限制了它们的实际应用,所以近年来众多非贵金属助催化剂(例如MoS_2,WS2,NiS,NiO和WC等)得到了广泛关注.由于非贵金属助催化剂存在弱电导率和低功函数等问题,影响了对光生电子的收集和利用.纳米碳材料具有极高的电导率、强可见光吸收、有效的载流子分离和较多的反应位点等优点,因此组合纳米碳材料和非贵金属助催化剂被认为是一种有效的解决方案.本文首次采用炭黑和NiS_2作为双助催化剂改性CdS纳米片,通过简单的溶剂热/沉淀两步法成功合成了廉价高效的CdS/CB/NiS_2三元光催化体系.光催化产氢性能测试表明,CdS-0.5%CB-1%NiS_2展现出最高的光催化效率(166.7μmol h~(-1)),分别是CdS NSs和CdS-1.0%NiS_2的5.16和1.87倍.X射线衍射、高分辨电子显微镜和X射线光电子能谱结果证实了CdS催化剂的片状结构,且炭黑和NiS_2成功负载在CdS纳米片表面.紫外-可见漫反射结果表明,随着炭黑和NiS_2的负载,复合催化剂的吸收边缘产生明显的红移,且对可见光的吸收增强.荧光光谱、阻抗和瞬态光电流曲线测试结果证明,炭黑和NiS_2的加入可以有效地促进光生电子/空穴对分离.极化曲线结果表明,加入炭黑和NiS_2可以降低CdS的产氢过电势,因此加速表面产氢动力学.总之,炭黑和NiS_2之间显著的协同效应极大地提高了可见光吸收,促进光生电子/空穴对分离,加速表面产氢动力学,最终得到了三元光催化体系极高的光催化产氢活性.     

Application of fractional calculus methods to asymmetric dynamical response of CB-Filled rubber

Frequency-sweep tests at various temperatures were conducted to study the asymmetric dynamic response of carbon black (CB) filled rubber. The master curves of storage modulus were constructed by use of time-temperature superposition (TTS), and the dynamic response of the material over a wide range of frequencies covering about 20 decades exhibits asymmetry. Based on the experimental results, the fractional Zener model and Prony series are verified to be unsuitable to reproduce the dynamicviscoelastic behavior. Therefore, a modified model by adding a spring-pot into the fractional Zener model is presented. The applicability of the modified model in describing the dynamic behavior of the CB-filled rubber is validated by the experimental results.