The chemical composition and antimicrobial activity of essential oils obtained from leaves of two Myrtaceae species-Eugenia uniflora L. and Plinia trunciflora (O. Berg) Kausel-were determined. Analysis by GC/MS as well as determination of Kovatz indexes indicated atractylone (26.78%) and curzerene (17.96%) as major constituents of E. uniflora oil and α-cadinol (19.15%), apiole (11.15%) and cubenol (5.43%) as main components in P. trunciflora oil. Both essential oils were tested for antimicrobial activity against yeasts and bacteria. E. uniflora and P. trunciflora essential oils were active towards two Gram-positive bacteria, Streptococcus equi and Staphylococcus epidermis. In addition, biological activity of both essential oils was detected for pathogenic yeasts of the genus Candida and Cryptococcus. E. uniflora was active towards all yeast tested and exhibited interesting minimal inhibitory concentrations (0.11 to 3.75 mg/mL) across a broad spectrum of activity. 相似文献
A biomimetic sensor for the determination of dipyrone was prepared by modifying carbon paste with cobalt phthalocyanine (CoPc), and used as an amperometric detector in a flow injection analysis (FIA) system. The results of cyclic voltammetry experiments suggested that CoPc behaved as a biomimetic catalyst in the electrocatalytic oxidation of dipyrone, which involved the transfer of one electron. The optimized FIA procedure employed a flow rate of 1.5 mL min−1, a 75 μL sample loop, a 0.1 mol L−1 phosphate buffer carrier solution at pH 7.0 and amperometric detection at a potential of 0.3 V vs. Ag/AgCl. Under these conditions, the proposed method showed a linear response for dipyrone concentrations in the range 5.0 × 10−6-6.3 × 10−3 mol L−1. Selectivity and interference studies were carried out in order to validate the system for use with pharmaceutical and environmental samples. In addition to being environmentally friendly, the proposed method is a sensitive and selective analytical tool for the determination of dipyrone. 相似文献
Structural Chemistry - In the original published version of the article, some typos are in the text, being in disagreement with the information found in Tables 1, 2, 3 and 4 and in the... 相似文献
We present a low‐cost mechanized system fabricated using fused deposition modelling 3D‐printing technology to manipulate microvolumes and perform injections on an electrochemical cell in wall‐jet configuration. As a proof‐of‐concept, the amperometric detection of paracetamol (model analyte) on a screen‐printed electrode using 0.5 μL aliquots resulted in highly reproducible responses (RSD <3 %). Moreover, handling of microliter aliquots of butylhydroxytoluene (phenolic antioxidant) and 2,2‐diphenyl‐2‐picrylhydrazyl (DPPH) to promote the radical‐scavenging reaction to determine antioxidant capacity by electrochemical detection of residual DPPH was demonstrated (time‐controlled reaction). A final application of the system was devoted to the analysis of cocaine and a common adulterant found in seized samples. The mechanized 3D‐printed analytical platform is capable to execute diverse sample preparation steps on board by handling microliter aliquots and subsequent electrochemical detection. 3D‐printing technology enabled the fabrication of a versatile and low‐cost (<U$200) mechanized system accessible to general chemistry labs. 相似文献
The full spectrum of two‐dimensional fermion states in a scalar soliton trap with a Lorentz breaking background is investigated in the context of graphene, where the Lorentz symmetry should not be strictly valid. The field theoretical model with Lorentz breaking terms represents Dirac electrons in one valley and in a scalar field background. The Lorentz violation comes from the difference between the Dirac electron and scalar mode velocities, which should be expected when modelling the electronic and lattice excitations in graphene. Here, only one Lorentz‐violating parameter is considered, belonging to the scalar sector. The analytical methods developed in the context of 1+1 field theories are extended to explore the effect of the Lorentz symmetry breaking in the charge carrier density of two‐dimensional materials in the presence of a domain wall with a kink profile. The width and the depth of the trapping potential from the kink is controlled by the Lorentz violating term, which is reflected analytically in the band structure and properties of the trapped states. These findings enlarge previous studies of the edge states obtained with domain wall and in strained graphene nanoribbon in a chiral gauge theory. 相似文献
A class of oscillating Lorentz-covariant configurations for the evolution of the domain walls in diverse dimensions are analytically obtained. It is shown that the oscillating solutions in the case of domain walls are responsible for structures which are larger than the usual kink-like configurations and, in the Lorentz-covariant evolution case, lead to long-standing configurations. 相似文献
Polymeric materials are present in various industrial sectors and in daily life, presenting advantages such as low cost and durability. Several processes for manufacturing have been developed. To achieve safety and operational goals measurement methods for proper process monitoring and effective control are needed. However, in real polymer plants, measuring devices are subject to uncertainties and are not always available. Hence, this paper proposes a virtual sensor scheme based on a particle filter and artificial neural network (ANN) that is applied to a simulated polymerization reactor. This scheme reduces uncertainties and enables the observation of latent variables. The ANN is also used for predicting the final properties of the polymer. The goal is to provide controllers with more complete and improved information. The results show that the virtual sensor scheme improves the process control, providing accurate estimates and action times that are consistent with industrial sampling intervals, which highlights its potential for practical applications.