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631.
Aprea E Gika H Carlin S Theodoridis G Vrhovsek U Mattivi F 《Journal of chromatography. A》2011,1218(28):4517-4524
A headspace SPME GC-TOF-MS method was developed for the acquisition of metabolite profiles of apple volatiles. As a first step, an experimental design was applied to find out the most appropriate conditions for the extraction of apple volatile compounds by SPME. The selected SPME method was applied in profiling of four different apple varieties by GC-EI-TOF-MS. Full scan GC-MS data were processed by MarkerLynx software for peak picking, normalisation, alignment and feature extraction. Advanced chemometric/statistical techniques (PCA and PLS-DA) were used to explore data and extract useful information. Characteristic markers of each variety were successively identified using the NIST library thus providing useful information for variety classification. The developed HS-SPME sampling method is fully automated and proved useful in obtaining the fingerprint of the volatile content of the fruit. The described analytical protocol can aid in further studies of the apple metabolome. 相似文献
632.
We consider optical propagation through a centrosymmetric photorefractive crystal with the externally applied bias voltage modulated along the optical propagation direction. We analytically prove that, if the modulation scale is smaller than the optical diffraction length, the resulting effective nonlinearity has an even parity in the transverse plane for an even-symmetric intensity profile and supports bending-free solitons down to few-micrometer beam widths. Numerical integration of the full photorefractive model for light-matter interaction allows us to confirm the feasibility of these miniaturized solitons and, for longer modulation periods, to investigate the excitation of self-trapped wiggling optical beams. 相似文献
633.
Natalya V. Likhanova Diego Guzmán-Lucero Eugenio A. Flores Paloma García Marco A. Domínguez-Aguilar Jorge Palomeque Rafael Martínez-Palou 《Molecular diversity》2010,14(4):777-787
Seventy five ionic liquids (ILs) were tested as a sequestering agent of sulfured compounds in natural gasoline (NG). Desulphurization
of NG was performed by means of liquid–liquid extraction method at room temperature and atmospheric pressure. Experimental
ILs containing imidazolium, pyridinium, and ammonium cations along with organic and inorganic anions were synthesized conventionally
and under microwave and sonochemical conditions. The effect of the molecular structure of ILs on the desulfurization efficiency
of NG with high sulfur content was evaluated. Analysis indicated that the anion type played a more important role than the
cation on the desulphurization process. ILs based on halogen–ferrates and halogen–aluminates exhibited the highest efficiency
in sulfur removal, and their efficiency is further improved when there is an excess of metallic salt in a ratio of at least
1:1.3 during the synthesis of the corresponding IL. An explanation for the ability of metallic ILs to remove sulfur-containing
compounds from natural gasoline based on the ratio of the ionic charge to the atomic radius is proposed. Furthermore, a method
to recover and reuse water-sensitive to halogenated precursors is described. 相似文献
634.
635.
Eugenio Costamagna 《Nonlinear dynamics》2018,93(1):119-132
This study is concerned with forced damped purely nonlinear oscillators and their behaviour at different excitation frequencies. First, their dynamics is considered numerically for the response determined in the vicinity of a backbone curve with the aim of detecting coexisting responses that have not been found analytically so far. Both the cases of low and high excitation amplitudes are investigated. Second, the angular excitation frequency is lowered significantly for different powers of nonlinearity, and the system’s behaviour is examined qualitatively, which has not been considered previously related to a general class of purely nonlinear oscillators. It is illustrated that the response at a low-valued angular excitation frequency has a form of bursting oscillations, consisting of fast oscillations around a slow flow. Finally, approximate analytical solutions are presented for the slow and fast flow for a general class of purely nonlinear oscillators. 相似文献
636.
Noemi Monni Jos J. Baldoví Víctor García-Lpez Mariangela Oggianu Enzo Cadoni Francesco Quochi Miguel Clemente-Len Maria Laura Mercuri Eugenio Coronado 《Chemical science》2022,13(25):7419
By combining 3,6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone (H2trz2An) with NIR-emitting ErIII ions, two different 3D neutral polymorphic frameworks (1a and 1b), differing in the number of uncoordinated water molecules, formulated as [Er2(trz2An)3(H2O)4]n·xH2O (x = 10, a; x = 7, b), have been obtained. The structure of 1a shows layers with (6,3) topology forming six-membered rings with distorted hexagonal cavities along the bc plane. These 2D layers are interconnected through the N4 atoms of the two pendant arms of the trz2An linkers, leading to a 3D framework, where neighboring layers are eclipsed along the a axis, with hexagonal channels filled with water molecules. In 1b, layers with (6,3) topology in the [101] plane are present, each ErIII ion being connected to three other ErIII ions through bis-bidentate trz2An linkers, forming rectangular six-membered cavities. 1a and 1b are multifunctional materials showing coexistence of NIR emission and field-induced slow relaxation of the magnetization. Remarkably, 1a is a flexible MOF, showing a reversible structural phase transition involving shrinkage/expansion from a distorted hexagonal 2D framework to a distorted 3,6-brickwall rectangular 3D structure in [Er2(trz2An)3(H2O)2]n·2H2O (1a_des). This transition is triggered by a dehydration/hydration process under mild conditions (vacuum/heating to 360 K). The partially dehydrated compound shows a sizeable change in the emission properties and an improvement of the magnetic blocking temperature with respect to the hydrated compound, mainly related to the loss of one water coordination molecule. Theoretical calculations support the experimental findings, indicating that the slight improvement observed in the magnetic properties has its origin in the change of the ligand field around the ErIII ion due to the loss of a water molecule.Tuning of luminescent and SIM properties is herein reported, in a novel flexible 3D anilato-based ErIII-MOF, displaying reversible shrinkage/expansion from a distorted hexagonal to a 3,6-brickwall rectangular structure. 相似文献
637.
Paolo Vacca Maria Grazia Maglione Carla Minarini Giovanna Salzillo Eugenio Amendola Dario Della Sala Alfredo Rubino 《Macromolecular Symposia》2005,228(1):263-272
In order to optimize polymer light emitting diode (PLED) performances, devices with holes injected through an Indium Tin Oxide (ITO) / Polyaniline (PANI) electrode into the polymer are much more efficient than devices fabricated with the anode made only by ITO. We demonstrated that by using doped PANI as hole injection layer in a polymer light emitting diode the manufacturing process can become simpler. Indeed, the pattern of conductive layer can be produced without ITO photolithography by UV exposition. As hole transporter layer, Poly(N-vinylcarbazole) (PVK) was spin coated over the doped PANI layer and a layer of tris (8-hydroxy) quinoline aluminum (Alq3) was then thermally evaporated so as to form the electron transport layer. To complete the device structure, Aluminum contacts were deposited onto the organic layers by vacuum evaporation at low pressure. The layers were characterized by X-ray small-angle diffraction, IR Raman and UV-Vis spectroscopies. Devices without PANI and with PANI as HIL were studied. 相似文献