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991.
Sol–gel derived xNb2O5–(100 ? x)SiO2 films (where x = 100, 80, 60, 50, 40, 20, 0 mol%) were nitrided at various temperatures (800 °C, 900 °C, 1000 °C, 1100 °C and 1200 °C). The structural transformations occurring in the films as a result of ammonolysis were studied using X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The XRD results have shown that the temperatures below 1100 °C were too low to obtain a pure NbN phase in the samples. The AFM observations indicate that the formation of the NbN phase and the size of NbN grains are related to the silica content in the layer. NbN grains become more regular and larger as the niobium content increases. The maximum grain size of about 100 nm was observed for x = 100. Preparation of the Nb2O5–SiO2 sol–gel derived layers and the subsequent nitridation is a promising method of inducing crystalline NbN in amorphous matrices. It follows from the XPS results that a small amount of Nb2O5 remains in the films after nitridation at 1200 °C and that nitrogen reacted not only with Nb2O5 but also with SiO2. 相似文献
992.
We demonstrate that a Peierls dimerization can occur in ferromagnetic spin chains activated by thermal fluctuations. The dimer order parameter and entanglement measures are studied as functions of the modulation of the magnetic exchange interaction and temperature, using a spin-wave theory and the density-matrix renormalization group. We discuss the case where a periodic modulation is caused by spin-phonon coupling and the case where electronic states effectively induce such a modulation. The importance of the latter for a number of transition metal oxides is highlighted. 相似文献
993.
M. Nabiałek J. Zbroszczyk J. Olszewski M. Hasiak W. Ciurzyńska K. Sobczyk J. Świerczek J. Kaleta A. Łukiewska 《Journal of magnetism and magnetic materials》2008
The microstructure and magnetic properties, i.e. the initial magnetic susceptibility, its disaccommodation, core losses and approach to ferromagnetic saturation of the bulk amorphous and partially crystallized Fe61Co10Zr2.5Hf2.5Nb2W2B20 alloy are studied. From X-ray, Mössbauer spectroscopy and electron microscopy studies we have stated that all samples in the as-quenched state are fully amorphous. However, after annealing the samples at 850 K for 30 min the crystalline α-FeCo grains embedded in the amorphous matrix are found. Moreover, from Mössbauer spectra analysis we have stated that the crystalline phase in those samples exhibits the long-range order. The alloy in the as-quenched state shows good thermal stability of the initial magnetic susceptibility. Furthermore, the intensity of the magnetic susceptibility disaccommodation in the rod is lower than in the ribbon. It is due to low quenching rate during the rod preparation which involves the reduction of free volumes. From the analysis of the isochronal disaccommodation curves, assuming the Gaussian distribution of relaxation times, we have found that activation energies of the elementary processes responsible for this phenomenon range from 1.2 to 1.4 eV. After the annealing of the samples the initial susceptibility slightly enhances and disaccommodation drastically decreases. From high-field magnetization studies we have learned that the size of structural defects depends on the quenching rate (the shape of the samples) and changes after annealing. 相似文献
994.
We introduce a microscopic model which unravels the physical mechanisms responsible for the observed phase diagram of the RVO3 perovskites. It reveals a nontrivial interplay between superexchange, the orbital-lattice coupling due to the GdFeO3-like rotations of the VO6 octahedra, and orthorhombic lattice distortions. We find that the lattice strain affects the onset of the magnetic and orbital order by partial suppression of orbital fluctuations. The present approach also provides a natural explanation of the observed reduction of magnon energies from LaVO3 to YVO3. 相似文献
995.
Wojciech Smuek Przemysaw Siejak Farahnaz Fathordoobady ukasz Masewicz Yigong Guo Magorzata Jarzbska David D. Kitts Przemysaw ukasz Kowalczewski Hanna Maria Baranowska Jerzy Stangierski Anna Szwajca Anubhav Pratap-Singh Maciej Jarzbski 《Molecules (Basel, Switzerland)》2021,26(19)
The use of natural surfactants including plant extracts, plant hydrocolloids and proteins in nanoemulsion systems has received commercial interest due to demonstrated safety of use and potential health benefits of plant products. In this study, a whey protein isolate (WPI) from a byproduct of cheese production was used to stabilize a nanoemulsion formulation that contained hempseed oil and the Aesculus hippocastanum L. extract (AHE). A Box–Behnken experimental design was used to set the formulation criteria and the optimal nanoemulsion conditions, used subsequently in follow-up experiments that measured specifically emulsion droplet size distribution, stability tests and visual quality. Regression analysis showed that the concentration of HSO and the interaction between HSO and the WPI were the most significant factors affecting the emulsion polydispersity index and droplet size (nm) (p < 0.05). Rheological tests, Fourier transform infrared spectroscopy (FTIR) analysis and L*a*b* color parameters were also taken to characterize the physicochemical properties of the emulsions. Emulsion systems with a higher concentration of the AHE had a potential metabolic activity up to 84% in a microbiological assay. It can be concluded from our results that the nanoemulsion system described herein is a safe and stable formulation with potential biological activity and health benefits that complement its use in the food industry. 相似文献
996.
A. K. Kwaśniewski 《Advances in Applied Clifford Algebras》1999,9(2):249-260
The non commuting matrix elements of matrices from quantum groupGL
q
(2;C) withq≡ω being then-th root of unity are given a representation as operators in Hilbert space with help ofC
4
(n)
generalized Clifford algebra generators appropriately tensored with unit 2×2 matrix infinitely many times. Specific properties
of such a representation are presented. Relevance of generalized Pauli algebra to azimuthal quantization of angular momentum
alà Lévy-Leblond [10] and to polar decomposition ofSU
q
(2;C) quantum algebra alà Chaichian and Ellinas [6] is also commented.
The case ofq∈C, |q|=1 may be treated parallely. 相似文献
997.
ukasz Kuterasiski Mariusz Gackowski Jerzy Podobiski Dorota Rutkowska-Zbik Jerzy Datka 《Molecules (Basel, Switzerland)》2021,26(20)
One of the methods of IR studies of the heterogeneity of Si–OH–Al groups in zeolites is the investigation of the frequency shift of the band of free OH bands restored upon the adsorption of ammonia and subsequent desorption at increasing temperatures. We extended this method by following the shift of the band of the OH group interacting by hydrogen bonding with nitrogen. The advantage of nitrogen, compared with CO, which has been commonly used as a probe molecule in studies on hydrogen bonding, is that for nitrogen the frequency shift is smaller than for CO and therefore there is no overlapping of shifted OH band with the bands of ammonium ions. For zeolites NaHY, HMFI, and HBEA, the frequency shift of IR bands of both free and hydrogen-bonded Si–OH–Al with the increase of ammonia desorption temperature evidences the heterogeneity of these hydroxyls. On the other hand, in zeolite HFAU of Si/Al = 31, Si–OH–Al were found to be homogeneous. Heterogeneity of OH groups may be explained both by the presence of Si–OH–Al of various number of Al near the bridge and of Si–OH–Al of various geometry. 相似文献
998.
999.
Urszula Krupa-Kozak Natalia Bczek Vanessa D. Capriles ukasz opusiewicz 《Molecules (Basel, Switzerland)》2022,27(9)
The food industry generates a great amount of food waste and by-products, which in many cases are not fully valorized. Press cakes, deriving from oilseeds extraction, represent interesting co-products due to their nutritional value, high biopolymers content, and the presence of bioactive phytochemicals. Gluten-free breads (GFBs) are products that have disadvantages such as unsatisfactory texture, low nutritional value, and short shelf life, so natural additives containing proteins and hydrocolloids are in demand to increase GFBs value. In this study, extract from flaxseed by-product (FOCE—Flaxseed Oil Cake Extract) was used to replace water (25–100%) in GFBs formulations and their nutritional value, antioxidant properties, and sensory features were investigated. The results showed that GFBs with FOCE had an elevated nutritional and nutraceutical profile (up to 60% more proteins, significantly increased K, Mg, and P levels). Moreover, the addition of FOCE improved the technological parameters (increased specific volume, number of cells and height/width ratio, reduced density, average size, and perimeter of cells), antioxidant potential, and overall sensory quality of GFBs. This study showed an encouraging way of using a by-product that, due to its high content of proteins, polysaccharides, minerals, and antioxidants, can add value to GFBs. 相似文献
1000.
Robert P. Sarzała Łukasz Piskorski 《Applied Physics A: Materials Science & Processing》2011,102(2):359-366
The comprehensive optical-electrical-thermal-recombination self-consistent VCSEL model is used to compare the performance
of oxide-confined (OC) and proton-implanted (PI) VCSELs and to optimise their structures. Generally index-guided (IG) OC VCSELs
demonstrate lower lasing thresholds whereas both gain-guided (GG) OC and PI ones manifest much better mode selectivity. Therefore,
their either low-threshold IG or mode-selective GG versions may be intentionally used for different VCSEL applications. Lasing
thresholds of OC IG VCSELs have been found to be very sensitive to the exact localisation of their thin oxide apertures, which
should be shifted as close as possible towards the anti-node position. PI VCSELs, on the other hand, are simpler and cheaper
in their manufacturing than OC ones. Although lower threshold currents are manifested by PI VCSELs with very thick implanted
regions, lower threshold powers are achieved in these devices with much thicker upper unaffected layer used for the radial
current flow from the ring contact towards the laser axis. Paradoxically poor thermal properties of PI VCSELs enable lower
lasing thresholds of slightly detuned devices. To conclude, cheaper and mode-selective PI VCSELs may be used instead of OC
ones in many of their applications provided ambient temperatures and laser outputs are not too high. 相似文献