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81.
82.
The objective was to investigate the effect of stall partition design on total lying time, lying position, and stall cleanliness, and to evaluate the preferences of cows regarding stalls with traditional fixed stall dividers or flexible stall dividers. Using a crossover design, 16 nonlactating dairy cows were housed singly for 9 d in pens with 2 freestalls, 1 with fixed cantilever dividers and 1 with flexible dividers. The cows were first given access to one stall type, and then to the other type of stall, and finally to both in a preference test. Type of stall divider did not influence lying behavior (13.5 h for fixed versus 14.0 h for flexible, ± 0.4 h), lying positions, or stall cleanliness; however, the cows showed a preference for lying in the flexible stalls (65.2 for flexible vs. 34.8 for fixed ± 8.2%). This indicated that cows are able to distinguish between type of stall divider and that it is important to them; however, it is not clear if the reason for this is the shape or the properties of the dividers. We concluded that cattle chose a flexible stall divider over a fixed one, but the long-term consequences of this preference are not clear, because no obvious changes in stall usage were observed when cows were only given access to one type of divider. 相似文献
83.
Optimized spatial correlations for broadband light trapping nanopatterns in high efficiency ultrathin film a-Si:H solar cells 总被引:1,自引:0,他引:1
Nanophotonic structures have attracted attention for light trapping in solar cells with the potential to manage and direct light absorption on the nanoscale. While both randomly textured and nanophotonic structures have been investigated, the relationship between photocurrent and the spatial correlations of random or designed surfaces has been unclear. Here we systematically design pseudorandom arrays of nanostructures based on their power spectral density, and correlate the spatial frequencies with measured and simulated photocurrent. The integrated cell design consists of a patterned plasmonic back reflector and a nanostructured semiconductor top interface, which gives broadband and isotropic photocurrent enhancement. 相似文献
84.
Organic small molecules are of particular interest for medicinal chemistry since they comprise many biologically active compounds which are potential drugs. To understand this vast chemical space, we are enumerating all possible organic molecules to create the chemical universe database GDB, which currently comprises 977 million molecules up to 13 atoms of C, N, O, Cl and S. Furthermore, we have established a simple classification method for organic molecules in form of the MQN (molecular quantum numbers) system, which is an equivalent of the periodic system of the elements. Despite its simplicity the 42 dimensional MQN system is surprisingly relevant with respect to bioactivity, as evidenced by the fact that groups of biosimilar compounds form close groups in MQN space. The MQN space of the known organic molecules in PubChem and of the unknown molecules in the Chemical Universe Database GDB-13 can be searched interactively using browser tools freely accessible at www.gdb.unibe.ch. 相似文献
85.
Jurriaan Boon Eric van Dijk Özlem Pirgon-Galin Wim Haije Ruud van den Brink 《Catalysis Letters》2009,131(3-4):406-412
Kinetics of the water–gas shift reaction over a FeCr-based catalyst is measured with high and low extremes for CO2 and H2 content and containing 11–35 ppmv of H2S, relevant for separation-enhanced water–gas shift in IGCC. Kinetics is well described by a power rate law. H2S negatively affects the reaction rate. Comparison with literature shows a more elaborate kinetic model is better suited to fully capture kinetics from sulphur-free to high-sulphur. 相似文献
86.
We present the synthesis of tungsten oxide (WO3−x) thin films consisting of layers of varying oxygen content. Configurations of layered thin films comprised of W, W/WO3−x, WO3/W and WO3/W/WO3−x are obtained in a single continuous hot-wire chemical vapor deposition process using only ambient air and hydrogen. The air oxidizes resistively heated tungsten filaments and produces the tungsten oxide species, which deposit on a substrate and are subsequently reduced by the hydrogen. The reduction of tungsten oxides to oxides of lower oxygen content (suboxides) depends on the local water vapor pressure and temperature. In this work, the substrate temperature is either below 250 °C or is kept at 750 °C. A number of films are synthesized using a combined air/hydrogen flow at various total process pressures. Rutherford backscattering spectrometry is employed to measure the number of tungsten and oxygen atoms deposited, revealing the average atomic compositions and the oxygen profiles of the films. High-resolution scanning electron microscopy is performed to measure the physical thicknesses and display the internal morphologies of the films. The chemical structure and crystallinity are investigated with Raman spectroscopy and X-ray diffraction, respectively. 相似文献
87.
Hassan Sawalha Giel Margry Ruud den Adel Paul Venema Arjen Bot Eckhard Flöter Erik van der Linden 《European Journal of Lipid Science and Technology》2013,115(3):295-300
Mixtures of γ‐oryzanol and β‐sitosterol were used to structure different oils (decane, limonene, sunflower oil, castor oil, and eugenol). The γ‐oryzanol and β‐sitosterol mixtures self‐assemble into double‐walled hollow tubules (~10 nm in diameter) in the oil phase, which aggregate to form a network resulting in firm organogels. The self‐assembly of the sterol molecules into tubules was studied using light scattering and rheology. By using different oils, the influence of the polarity of the oil on the self‐assembly was studied. The effects of temperature and structurant concentration on the tubuler formation process were determined and the thermodynamic theory of self‐assembly was applied to calculate the change in Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) resulting from the aggregation of the structurants was determined. The self‐assembly was found to be enthalpy‐driven as characterized by a negative ΔH0 and ΔS0. A decreasing polarity of the oil promotes the self‐assembly leading to formation of tubules at higher temperatures and lower structurant concentrations. 相似文献
88.
Wilfried GJHM van Sark Jessica de Wild Jatin K Rath Andries Meijerink Ruud EI Schropp 《Nanoscale research letters》2013,8(1):81
The possibility to tune chemical and physical properties in nanosized materials has a strong impact on a variety of technologies, including photovoltaics. One of the prominent research areas of nanomaterials for photovoltaics involves spectral conversion. Modification of the spectrum requires down- and/or upconversion or downshifting of the spectrum, meaning that the energy of photons is modified to either lower (down) or higher (up) energy. Nanostructures such as quantum dots, luminescent dye molecules, and lanthanide-doped glasses are capable of absorbing photons at a certain wavelength and emitting photons at a different (shorter or longer) wavelength. We will discuss upconversion by lanthanide compounds in various host materials and will further demonstrate upconversion to work for thin-film silicon solar cells. 相似文献
89.
Investigating alternative routes for semi‐aromatic polyamide salt preparation: The case of tetramethylenediammonium terephthalate (4T salt)
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Athanasios Porfyris Stamatina Vouyiouka Constantine Papaspyrides Ruud Rulkens Eric Grolman Geert Vanden Poel 《应用聚合物科学杂志》2016,133(13)
In the current article, the effect of different techniques was investigated on the preparation of tetramethylenediammonium terephthalate (4T salt), which consists of an industrially important precursor of high‐performance polyamides. In particular, 4T salt was synthesized through solution, slurry, and solvent‐free techniques. In each case the salt was isolated as a solid, correlating for the first time the salt preparation/isolation method with attained properties and morphology. This correlation led to a generalized comparison between all synthesized 4T salt grades, aiming at understanding the preparation mechanism of 4T salt. Accordingly, highly pure 4T salt, free of any unreacted diacid traces, can be only obtained from a clear salt solution either by cooling or by nonsolvent addition. Furthermore, by altering the crystallization conditions of the salt, thermal and morphological properties can be significantly affected, which further result in a qualitative correlation with the rate of subsequent direct solid‐state polymerization (DSSP). The DSSP reactions were carried out in the microscale of a thermogravimetric chamber, where the different 4T salt grades were heated isothermally until full conversion. Polyamide grades of different thermal and analytical properties were received, underlining that the quality of the salt is a corner stone for subsequent DSSP. These findings can be further exploited also to the DSSP of other semi‐aromatic polyamides. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42987. 相似文献
90.
A MEMS‐based heating holder for the direct imaging of simultaneous in‐situ heating and biasing experiments in scanning/transmission electron microscopes
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Luigi Mele Stan Konings Pleun Dona Francis Evertz Christoph Mitterbauer Pybe Faber Ruud Schampers Joerg R. Jinschek 《Microscopy research and technique》2016,79(4):239-250
The introduction of scanning/transmission electron microscopes (S/TEM) with sub‐Angstrom resolution as well as fast and sensitive detection solutions support direct observation of dynamic phenomena in‐situ at the atomic scale. Thereby, in‐situ specimen holders play a crucial role: accurate control of the applied in‐situ stimulus on the nanostructure combined with the overall system stability to assure atomic resolution are paramount for a successful in‐situ S/TEM experiment. For those reasons, MEMS‐based TEM sample holders are becoming one of the preferred choices, also enabling a high precision in measurements of the in‐situ parameter for more reproducible data. A newly developed MEMS‐based microheater is presented in combination with the new NanoEx?‐i/v TEM sample holder. The concept is built on a four‐point probe temperature measurement approach allowing active, accurate local temperature control as well as calorimetry. In this paper, it is shown that it provides high temperature stability up to 1,300°C with a peak temperature of 1,500°C (also working accurately in gaseous environments), high temperature measurement accuracy (<4%) and uniform temperature distribution over the heated specimen area (<1%), enabling not only in‐situ S/TEM imaging experiments, but also elemental mapping at elevated temperatures using energy‐dispersive X‐ray spectroscopy (EDS). Moreover, it has the unique capability to enable simultaneous heating and biasing experiments. Microsc. Res. Tech. 79:239–250, 2016. © 2016 Wiley Periodicals, Inc. 相似文献