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991.
Zarzycki PK Zarzycka MB Clifton VL Adamski J Głód BK 《Journal of chromatography. A》2011,1218(33):5694-5704
The goal of this paper is to demonstrate the separation and detection capability of eco-friendly micro-TLC technique for the classification of spirulina and selected herbs from pharmaceutical and food products. Target compounds were extracted using relatively low-parachor liquids. A number of the spirulina samples which originated from pharmaceutical formulations and food products, were isolated using a simple one step extraction with small volume of methanol, acetone or tetrahydrofuran. Herb samples rich in chlorophyll dyes were analyzed as reference materials. Quantitative data derived from micro-plates under visible light conditions and after iodine staining were explored using chemometrics tools including cluster analysis and principal components analysis. Using this method we could easily distinguish genuine spirulina and non-spirulina samples as well as fresh from expired commercial products and furthermore, we could identify some biodegradation peaks appearing on micro-TLC profiles. This methodology can be applied as a fast screening or fingerprinting tool for the classification of genuine spirulina and herb samples and in particular may be used commercially for the rapid quality control screening of products. Furthermore, this approach allows low-cost fractionation of target substances including cyanobacteria pigments in raw biological or environmental samples for preliminary chemotaxonomic investigations. Due to the low consumption of the mobile phase (usually less than 1 mL per run), this method can be considered as environmentally friendly analytical tool, which may be an alternative for fingerprinting protocols based on HPLC machines and simple separation systems involving planar micro-fluidic or micro-chip devices. 相似文献
992.
993.
In the present work, the effect of individual additives calculated as molar fractions of Sb2O3 and CeO2 (x
Sb
2O3 range: 0.03–0.08 %, x
CeO
2 range: 0.05–0.14 %), on the phase composition, phase transformation, and optical properties of photostable rutile titanium
dioxide was studied using selective leaching method, ICP-AES technique, XRD method, spectrophotometric analysis and S
BET measurements. The starting material was hydrated titanium dioxide. It was observed that the addition of Sb2O3 to TiO2 did not influence the anatase-rutile phase transformation, but increasing the CeO2 addition caused a decrease in the rutilization degree. Thus, CeO2 acted as an inhibitor of the TiO2 phase transformation. Sb2O3 addition to TiO2 presumably caused the formation of a co-phase of Sb with Ti. Cerium formed a separate phase, CeO2, and reacted partly with titanium, probably creating co-phase, Ce0.8Ti0.2O2. Comparing the colour of modified rutile titanium dioxide according to the type of the additive introduced, it was found
that TiO2 with CeO2 had higher brightness but lower white tone values when compared with TiO2 modified with Sb2O3. The relative lightening power and grey tone of the modified TiO2 were higher in TiO2 modified with Sb2O3. The values of the photocatalytic activity measured in all TiO2 samples modified either with Sb2O3 or CeO2 were very similar and varied around the value of 21. 相似文献
994.
Jaworska A Wietecha-Posłuszny R Woźniakiewicz M Kościelniak P Malek K 《The Analyst》2011,136(22):4704-4709
The potential use of surface Raman enhanced spectroscopy (SERS) for confirmatory identification and the semi-quantitative analysis of selected tricyclic antidepressants (TCAs) is examined utilizing a conventional silver colloid. Raman and SERS spectra of aqueous solutions of imipramine (Imi) and its metabolite, desipramine (Des), were recorded as the function of concentration using NIR excitation. A good linear correlation is observed for the dependence of the SERS signal at 684 cm(-1) (R(2) = 0.9997) on Imi concentration over the range of 0.75-7.5 μM. The limit of detection of imipramine in the silver colloidal solution is 0.98 μM. SERS spectra of Imi and Des were also recorded for blood plasma samples without prior purification as well as after the use of standard solid phase extraction. All spectra show the characteristic spectral profile of the molecules and moreover, stronger signal enhancement is observed for Imi in the "raw" samples as opposed to Imi extracted from a biological matrix. 相似文献
995.
The geometry of spaces with indefinite inner product, known also as Krein spaces, is a basic tool for developing Operator
Theory therein. In the present paper we establish a link between this geometry and the algebraic theory of *-semigroups. It
goes via the positive definite functions and related to them reproducing kernel Hilbert spaces. Our concern is in describing
properties of elements of the semigroup which determine shift operators which serve as Pontryagin fundamental symmetries. 相似文献
996.
Adam Bartoszek Rémi Langevin Paweł G. Walczak 《Bulletin of the Brazilian Mathematical Society》2011,42(2):301-320
Canal surfaces defined as envelopes of 1-parameter families of spheres, can be characterized by the vanishing of one of the conformal principal
curvatures. We distinguish special canals which are characterized by the fact that the non-vanishing conformal principal curvature is constant along the characteristic
circles and show that they are conformally equivalent to either surfaces of revolution, or to cones over plane curves, or
to cylinders over plane curves, so they are isothermic. 相似文献
997.
Krzysztof Gawȩdzki Rafał R. Suszek Konrad Waldorf 《Communications in Mathematical Physics》2011,302(2):513-580
We revisit the gauging of rigid symmetries in two-dimensional bosonic sigma models with a Wess-Zumino term in the action.
Such a term is related to a background closed 3-form H on the target space. More exactly, the sigma-model Feynman amplitudes of classical fields are associated to a bundle gerbe with connection of curvature H over the target space. Under conditions that were unraveled more than twenty years ago, the classical amplitudes may be coupled
to the topologically trivial gauge fields of the symmetry group in a way which assures infinitesimal gauge invariance. We
show that the resulting gauged Wess-Zumino amplitudes may, nevertheless, exhibit global gauge anomalies that we fully classify.
The general results are illustrated on the example of the WZW and the coset models of conformal field theory. The latter are
shown to be inconsistent in the presence of global anomalies. We introduce a notion of equivariant gerbes that allow an anomaly-free coupling of the Wess-Zumino amplitudes to all gauge fields, including the ones in non-trivial
principal bundles. Obstructions to the existence of equivariant gerbes and their classification are discussed. The choice
of different equivariant structures on the same bundle gerbe gives rise to a new type of discrete-torsion ambiguities in the
gauged amplitudes. An explicit construction of gerbes equivariant with respect to the adjoint symmetries over compact simply
connected simple Lie groups is given. 相似文献
998.
Michał Cichomski Witold Szmaja 《Applied Physics A: Materials Science & Processing》2011,102(2):339-343
Polycrystalline cobalt films 100 nm thick were thermally evaporated on oxidized Si(100) substrates. Then 1H, 1H, 2H, 2H perfluorodecyltrichlorosilane
(FDTS) films of various thicknesses, in the range of about 2 nm to 30 nm, were grown on cobalt surfaces by vapor phase deposition
(VPD). The cobalt films modified by FDTS were investigated using magnetic force microscopy (MFM) and atomic force microscopy
(AFM). MFM observation showed that the magnetic structure of the cobalt films modified by FDTS is composed of domains with
a considerable component of magnetization perpendicular to the film surface. This in turn indicates that the cobalt films
on oxidized Si(100) substrates crystallize in the hexagonal close-packed (HCP) phase and exhibit a texture with the hexagonal
axis perpendicular to the film surface. The magnetic domains formed a maze structure. The domain width increased from typically
80–120 nm to 400–500 nm with increasing the thickness of FDTS films from about 2 nm to 30 nm. AFM imaging of the surfaces
of FDTS films revealed the presence of an agglomerate morphology. The agglomerates varied in size from typically 30–70 nm
to 150–300 nm as the film thickness was increased from about 2 nm to 30 nm. 相似文献
999.
For a given pure state of a composite quantum system we analyze the product of its projections onto a set of locally orthogonal separable pure states. We derive a bound for this product analogous to the entropic uncertainty relations. For bipartite systems the bound is saturated for maximally entangled states and it allows us to construct a family of entanglement measures, we shall call collectibility. As these quantities are experimentally accessible, the approach advocated contributes to the task of experimental quantification of quantum entanglement, while for a three-qubit system it is capable to identify the genuine three-party entanglement. 相似文献
1000.
The damping of magnons in ultrathin metallic magnets is studied from first-principles. We contrast Fe/Cu(100) and Fe/W(110) systems for which the influence of the substrate on the magnon life time differs strongly. We introduce the concept of Landau map in momentum space to assess the role of different electronic states in the attenuation. The formation of electronic complexes localized at the film-substrate interface leads to hot spots in the Landau maps and enhances the damping. This finding allows tuning the attenuation of high-frequency magnetization dynamics in nanostructures. 相似文献